Sometimes you lose important data. An app update could go wrong, an iOS update could remove some apps, or your iPad could be stolen. Whatever the reason, it's helpful to know how you can restore from an iTunes or iCloud sync backup.
This guide will cover restoring from a previous iTunes backup, but the process is similar for iCloud backups. If you open the iTunes Preferences on your computer and select the Devices tab, you'll see a list of the most recent sync backups for each of your devices.
This should give you an idea of whether your previous backup contains the data you need. If it's fairly recent, there's hope you can recover nearly everything you thought you lost.
To restore, click the File menu and select Devices > Restore From Backup.
Apple's support site describes the process in detail (they're notorious for changing links, so if that doesn't work, search Google for "Back up and restore your iPhone, iPad, or iPod touch using iCloud or iTunes")