How much is my upper deck 1992 homerun heroes Frank Thomas worth?

You might be able to get a buck or two for it. You can get the entire set for less than $10

The answer above may be correct. But, it would be best if you would take the card to a store that sells collectible cards and have someone examine it there. So much of what a card is worth monetarily, greatly depends on the condition of the card or cards. Card collectors who trade or buy cards get very picky about even the smallest imperfection in a card as being determinants in the value of a card.