How do I find out how much a baseball card would be worth?

I have several cards, they say Baseball's all-time greats on the top. Doesn't say who they are by or when they were made. basically have info about the player like when and where they were born, how long they played, how many games, when they were inducted into the hall of fame and such. I have a Cy Young, Jackie Robinson, Babe Ruth, and Ty Cobb.