Take it to a comic book shop and talk to them about it. They don't deal in just comic books, they deal in cards too. Hope this helps.
How Much Is A Ken Griffey Jr. Rookie Card Worth?
About 50$
Topps
I have a topps rookie card
Donruss
Anywhere from $20 to $60 depending on condition.
75
You could buy a beckett book which has all of the cards on there and their estimated prices.hope this helps!
Its worth somewhere between $15 and $40 dollars if its still sealed in its pack...