How to prepare for a blizzard while trekking on a mountain pass?

I think that you yourself answered your question. If you know that there are often strong winds and blizzards on the pass, then it is better to set up your camp before or after the pass, it will be safer. Not only is there a strong wind and blizzards on the pass, but also the weather can change very quickly in the mountains. And if the weather changes quickly, then it is not always possible to be proactive. There can also be rockfalls, and this can quickly be more dangerous than even a strong wind. Therefore, I do not recommend putting up a tent on the pass. The task of the camp in the mountains is so high that it would be comfortable and safe to spend the night. But maybe you have a task or goal to spend the night on the pass itself?

We once in the Caucasus mountains and the Pamirs took several passes categorical. Therefore, what is strong wind, ice, rain and rockfalls in the mountains I know well)

Temperatures in winter hover around 14F to -10F. [...] Also the pass's top is known for it very high wind speeds and dangerous blizzards .

If the temperatures are at the low end of this range and there are high winds, then you're in an extremely challenging environment, and maintaining an appropriate level of safety while traveling alone will require deep experience. Plan your trip so that you can get a forecast close to the day you will be crossing this pass, and if the forecast is for low temps and high winds, be flexible about changing your plans, e.g., delaying crossing the pass.

I've heard that about 30 ft snow accumulates there during the whole winter and spring season.

If the area gets that much snow, and blizzards are frequent, then it raises serious danger from avalanche, especially if you cross this pass during the next few days after a big storm. Talk to locals who have experience with avalanche danger in this area. Don't travel on steep slopes (above about 30 degrees) soon after a storm, and plan how to avoid terrain traps. There are books and classes on avalanche safety.

Is it possible to camp(overnight) on such passes, or it is too risky.

Sounds like a bad idea, and why would you want to? A more normal plan for this sort of thing would be to position yourself close to the pass when you camp the night before, then get an early start and get up the pass in the early morning, while snow conditions are still firm. Then you come down the other side later in the day, and if conditions have softened up, it's OK on a descent.

The fact that there are blizzards means that you're in danger of getting disoriented. This is another reason to try to get a recent weather forecast before making the decision to cross on a particular day. Don't depend only on a phone's GPS. Bring a paper map, a compass, and a GPS unit that will work if your phone doesn't work, and make sure you know how to get coordinates off the GPS and find them on the paper map. Make sure you have lots of previous experience navigating with a paper topo map. There are classes that teach this.

Your question doesn't mention anything about crampons/microspikes and an ice ax. If conditions could turn icy, you'll need those, as well as the skills to use them correctly.

Snow camping isn't incredibly difficult, but it does require a certain set of skills. Listing gear won't prepare you if you don't have the skills. Mountaineering clubs and organizations such as the Sierra Club provide special classes on snow travel and snow camping. There are all kinds of detailed things to get experienced with, like how to deal with your water bottle freezing, and how to make sure your tent is anchored in the snow well enough to keep it from blowing away.

One thing you don't say in your question is how remote this area is. If there is a town or a ski resort 10 km from this pass, then that's one thing. If you're out in some remote region of British Columbia, 150 km from the nearest town, then safely traveling solo in winter is going to be a much bigger challenge.

You should camp lower down, if you are taking risk into account, as your answer implies you are. In the Sierra and Rockies, which is where I have experience, camping even a few hundred feet from the top will be very noticeably less windy, and you may even find a stone wind-break constructed by previous hikers.

If you go below timber line, you will find the ground level wind astonishingly reduced, and in the Sierra and Rockies, at least, timber line may not be all that far below 3,000 meters.

Some of the camping gear you need is obvious for cold, snow and wind and 3,000 meters (e.g., goggles, sun cream, spare socks and mitts, gaiters for your legs and also a neck gaiter, a strong tent, double sleeping pads (to avoid melting a shallow grave of ice in the snow from your body heat)), but I am not going to list everything. There is a good comment above on snowshoes. Finally...this is a solo trip, so be sure to take a PLB.

Finally, the question sounds as though you do not have much experience in winter conditions. Whether this is true or not, I can't tell.. If this is true, at least get some experience in camping in winter conditions before you go on this ambitious solo trip. Camping in winter is not merely colder, with longer nights, it is qualitatively different.