Sounds as if the solution to your problem is two-fold:
(1) Delete the app you have on your iPad that you didn't pay for and then go to the App Store and buy the app. Then, you won't have any trouble with updates in the future.
(2) Don't be a pirate! That's stealing and we do not condone that here at iPadForums.net. Please read the rules of this forum - they are very clear cut.
Noozie: Consider this a warning - no discussion (or any help with) pirated apps and any subsequent issues/problems.
Marilyn