do you really want to sell it? if you do, check to see how much you got it for which should be about $499 for the wi-fi only 16gb model, $599 for the 32gb, and $699 for the 64gb. just take off about $20 of the amount you paid for for that model.
If I were the buyer, I'd pay $175 because: A.) I don't know what mint condition is(Just Kidding!) B.) Because its from a couple of years ago I think now. If it were the Ipad 2 I'd pay $300 to $400 for it.