iPad reset

If you are selling or trading-in, follow this process to properly prepare the device. You will not lose any data synchronised to iCloud:

What to do before you sell, give away or trade in your iPhone, iPad or iPod touch – Apple Support

You will lose anything synced to other devices. That is why a back-up to your computer or an external drive is so important. Be sure to back-up important photos and data if you wish to keep them.

iCloud is a syncing service. Anything you delete from one device will be removed from all other devices. So it is not a suitable space for anything you want to be safe from deletion.