Yes, you won a $3,000 prize that you have to report as income on your tax return. The fact that the prize was donated makes no difference to you.
The radio station should send you a Form 1099-MISC with the amount of the prize in box 3. If they don't, enter it under Less Common Income > Prizes, Awards, and Gambling Winnings. Either way, read the questions carefully. If you did not pay anything to enter the contest, it's not gambling winnings, it's a prize.