I would like know which Cassette should I get for the Wahoo KICKR Core Smart Turbo Trainer
I own this cycle: Giant CONTEND 1 2017 – https://www.giant-bicycles.com/gb/contend-1-2017
It has a Rear Derailleur Shimano Sora. I first thought of getting the 11 Speed Cassette, but I believe this won’t compatible with the cycle due to the Rear Derailleur. Instead, I believe I should get the same Cassette as on my existing bike (SRAM PG 950 11×32)
Let me know what are my options when it comes to Cassette?
Will a 11 Speed Cassette work with existing Rear Derailleur Shimano Sora?
Unless you upgrade your shifter to 11 speeds, then you don't want to use an 11-speed cassette. The shifter, the derailleur, and the cassette all need to work together. So unless you plan to do that, use a 9-speed Shimano cassette.
You'll need to install a 1.85-mm spacer inboard of your 9-speed cassette on your Kickr. It may come with one (check the "what's in the box" details).
You could get a tighter cassette if you wanted. It doesn't need to be the same gearing. Conversely, you probably could get away with an 11-34. Also, if you'll be using your trainer primarily in erg mode, then it doesn't matter what your gears are.