I know very little about baseball cards but am willing to put forth the effort. Where is the best source to find their values, and sell them if any of them are worth any money?

I am going to be a junior this year. Right now i am 5′7 5′8ish and weight 160 pounds. Are there any workouts i should be doing to get ready for the season in the spring? I am planning on going on to play college baseball as well for a junior college team and i am just looking for some things that could help me out. I dont have the money to go buy fancy equipment or anything.

I have this box of baseball cards and don’t know who or where to ask to find out if they are worth any money. How can I find out?