how to remove activation lock if you cant reach old owner

Expanding upon comments of MichelPM...

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, or unless you can secure the cooperation of the previous owner, you’ll not be able to defeat or bypass the Activation Lock. Without documentary evidence that you are the original owner (such as sales receipt showing the serial number), Apple won’t assist - and nobody here will be able to help you.

The All Too Common SAD Reality of Buying … - Apple Community

You don't.

If you cannot reach the previous owner of this iPad to get the needed unlock info, then this iPad is a dead, useless device to you.

There is no way to bypass/circumvent user activation lock. None.

You will never get this iPad to ever work for you.

No one here can help you. Apple will NOT help you.

This iPad is a useless device to you.

Recycle this device responsibly.

Sorry.