I purchased an ipad at a resale shop and restored it. There is no way to contact the previous owner. I have a receipt for the purchase. What caaaan I do to use the ipad?

You cannot reset it without the original owner. Return it to the shop for a refund. The former owner failed to prepare it for sale or transfer per these Apple instructions:

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

The resale store should make themselves aware of Apple's anti-theft protections before selling any Apple device or stop dealing in them.

Go back to the shop and ask for a refund.

ChrisJ4203: It says in the title that there isn't a way to contact them.

(177808)

Thanks, I saw that, but was just saying that is the only method.

Contact the previous owner. They are the only one that can remove the Activation Lock. Without that, the device is useless to you. No one here, nor Apple can assist, since you are not the original purchaser.