It's probably worth about the same as what you paid for it back in the day. I found a 1991 Upper Deck complete set, unopened, for $15.
Anything that isn't before 1980 has absolutely no hope of being worth anything. Even rookie cards of today's big stars are rarely worth much. Another interesting thing - 1991 was the biggest year for baseball card sales. So 1991 cards have virtually no value.
Maybe they'll be worth something in 50 or 100 years when they're antiques and most have been thrown out or lost, or after the baseball card industry has died out completely.