Hey GeraldQ,
To reset your iPad back to factory settings, follow these steps from the article here: How to factory reset your iPhone, iPad, or iPod touch
You'll need to enter the Apple ID you used to set up your iPad. If you changed your Apple ID email, you can use that new email as long as it's the same account you had before.
Also, you can use a computer to erase your iPad. Follow these steps:
1. Connect your iPad to your computer with a USB or USB-C cable. You may also need an adapter. See Connect iPad and your computer with a cable.
2. Turn on your iPad.
3. Do one of the following:
On a Mac (macOS 10.15 or later): Click the Finder icon in the Dock to open a Finder window, click the iPad button in the Finder sidebar (below Locations), click General at the top of the window, then click Restore iPad.
On a Mac (macOS 10.14 or earlier) or a Windows PC: Make sure you have the latest version of iTunes (see the Apple Support article Update to the latest version of iTunes). Open iTunes, click the iPad button near the top left of the iTunes window, click Summary, then click Restore iPad.
You can find out more information here: Erase iPad
We hope this helps!
Best regards.