I believe the right command is

/give @p minecraft:(put weapon here){Unbreakable:1} 1

Instead of the command you did. You will have to move your "1" after minecraft:bow to after {unbreakable:1}. Tell me if this does not work and what error you get.

Your Problems

You have one problem and I have one suggestion.

Problem: You put the count before the nbt the syntax for the give command is the following.

/give <selector> <item>{<nbt>} <count>

So an example of the give command is the following.

/give @p minecraft:carrot_on_a_stick{Unbreakable:1} 1

My suggestion is to always specify the correct data type for your NBT tags. The Unbreakable tag is a Byte tag, and while it is okay to just type in a 1, the technical correct way is to specify a Byte: 1b

The Final Command

With the solutions specified, you get what follows.

/give @p minecraft:bow{Unbreakable:1b} 1

Being a programming language, Minecraft commands have some of the most nitpicky syntax and useless error messages. NBT in of itself is perhaps not too complicated, but Minecraft command syntax is not easy to learn for the simple reason that when you do something wrong, there is nearly no useful feedback.

If all you need to add is a single property (like unbreakable), then yes, the best choice is to do it manually, but it's worth noting there are other options, especially for more complex commands.

You can use a command generator like MCStacker to generate items with NBT tags much more simply. MCstacker has a lot of powerful tools for adding NBT and other useful features to vanilla commands.

MCstacker is not always that simple, but the first thing to do in your case would be to click on /give from the main menu, which that is a link to. After that, the first menu is to select what player you want to give the item to (It defaults to nearest player, but can be changed to anything Minecraft supports). Then, you can set any of the more complicated conditions to receive the item in the same section as the player or group who will revive them. After this, you can start making the item itself!

You can choose the item, in this case a bow, using the top drop-down box in the second grouping all the way at the bottom. After you select an item, in this case a bow, the grouping will get far bigger and have options for unbreakability, the name, the lore of the item,the current damage, the cost to repair in an anvil, enchantments, and more! There are several expanding windows, check boxes, and text boxes that are labeled with what they do.

Finally, to get your command, you can go to the top right corner and copy the text in the blue window. If it fails in your command line, that means it's too long and you need to run it in a command block.

Now you have your fully unbreakable bow with many enchantments, a custom name with cool colors, and even things that change the characteristics of the player.

or, you can just have unbreakable.

The syntax changed in 1.13 onward. You would use this now.

/give @p minecraft:bow{Unbreakable:1}

Before 1.13 you would use the original command.

/give @p minecraft:bow 1 0 {Unbreakable:1}