If you have an iCloud or iTunes backup, you will be able to restore the backup to your iPad. If the iPad has been reset/erased as described, you will need to setup the iPad again from the initial "hello" screen - and when prompted choose choose the backup from which you wish to restore your data and settings.
Turn on and set up iPad - Apple Support
If you have already setup the iPad, you can restore your data by following the appropriate process:
Restore all content to iPad from a backup - Apple Support
If you don't have a pre-existing backup, all data and documents that you have not previously synchronised with iCloud storage will have been irretrievably lost.