Hia ll,
I'm thinking about changing out the cassette on this old rim from an 8 sp. 11-30 to a 10 sp. 11-42. Instead of a new front single-chainring, I'll probably just run it on the 32T ring unless I want to goof around climbing up sides of buildings, or being able to pedal down ski slopes (humor).

Please don't tell me I should buy a used bike for $2,000 b/c it's "not worth" putting $50 into this experiment. Even an old bike will exceed my capabilities at this stage of life, and I am not going to be buying another.

I know nothing is universal, so I'm wondering how I pick out the appropriate cassette to fit the (?)hub that is on there.
Any suggestions in layperson's terms will be appreciated.

I may not know it all, but I am technically adept and pick up very quickly.