So, I haven't been able to do a chinup, or pull up (I'm not even sure what the difference is) since I was like 13. I'm 31 now, not much upper body strength. I'm female, 165 pounds.

I can't even do a full push up. I can do about 8 intermediate pushups down to floor and back up (girl pushup with feet elevated). I've been using dumbells to work my biceps and shoulders. What else should I do to work up to a chinup?

I can barely hang from the bar at this point, no glimmer of movement.
How much and how often should I be working my upper body?

When I can do like 20 full pushups, for example, will I be close to a chin up? Or are those different muscles?
Thanks for any insight!