If there's no way for you to remember your password you will have to erase your iPad and restore it to factory settings. To do that, go to Settings>General>Reset, then tap Erase All Content and Settings, this will restore your iPad to factory settings.Originally Posted by anautalik
If you have a backup that predates the time you added the password to your iPad, you can do a restore from backup through iTunes on your computer. If your backup was made after you added the password, you will have to set it up as a new iPad. Your content, such as movies, music and tv shows can be restored from the purchased list in iTunes. Your apps can be restored from the purchased list in the app store.
If you used iCloud, you should be able to recover the data stored there.