One that works. I think my PC is capable of another SSD, recently saw a slot that looks suspiciously like one when I was cleaning it. I don't know computers. I just have a 2TB HDD plugged into my PC that's dying from age (Got it in 2019... and has survived some insane abuse) as well as being full. Another 1TB SSD external but I use that for video games because I've only got 500GB internally.
I don't know computers I just know memes