You got sold an iPad with user Activation Lock.
You'll never, EVER get that iPad to work for you
This is a dead and useless device to you!
If you can, return this device and attempt to get your money back!
Purchase an iPad from a more reputable source and if you insist on buying used iPad's on eBay you need to ask a lot more questions of the seller and to see either or both more photos/images/short video showing a perfectly setup iPad with the initial animated “HELLO” screen in multi-languages moving across the screen as proof an iPad has been properly setup for sale and that their is NO iCloud activation lock, either!
With eBay, the more pointed questions you ask of the seller and the more images and videos they can supply, the better!
If the seller is being difficult about supplying more info and images and short videos of the iPad’s start up screen, move on to another iPad seller.
Sorry & Good Luck to You!