Sadly, as described, the iPad is (and will likely remain) useless to you.
Here are the Apple support pages that outline the Activation Lock - and the only mechanisms by which it can be turned off:
Activation Lock for iPhone, iPad, and iPod touch - Apple Support
Turn off Activation Lock – Apple Support
As you will discover, unless you are the owner of the AppleID that was last used to activate the device, you’ll not be able to defeat or bypass the Activation Lock. With documentary evidence that you are the original owner (such as sales receipt showing the serial number), Apple may be prepared to assist - otherwise they and nobody here will be able to help you.
If you have the necessary documentation, Apple have recently introduced a new portal though which you may be able to request release of an Activation Lock:
How to remove Activation Lock - Apple Support & start an Activation Lock support request.