If you forget the device screen lock passcode or the device is disabled, by explicit design, the one and the only mechanism to reset it requires you to erase the device. This ensures that nobody, no one at all, can regain access to a device with the data intact when they do not know the screen lock passcode. It is assumed that once reset, an owner will restore their data from an iCloud or iTunes backup. Your failure to backup your device means you’re now going to loose data. And their is no way around that.
Are you sure you’re device wasn’t using automatic iCloud backups? See -> Back up iPad - Apple Support
See instructions in -> If you forgot the passcode on your iPad, or your iPad is disabled - Apple Support