If the previous owner in not in contact then how can i remove activation lock from iPad?

You cannot. Activation Lock is an anti-theft mechanism designed to prevent just anyone from accessing the device.

If the previous owner did not remove their Apple ID from iCloud, and turned off Find My iPhone, and you cannot contact him now, there's not much you can do.

No, Apple will not get involved at all. The owner who sets up activation lock is responsible for removing activation lock when they dispose of their device. Apple doesn’t get involved with issues with buyers and second hand personal property. That’s between you and the seller.

No - you can’t “pay” to defeat this security measure 🙂

Nope.

You don't.

No one here can hekp you. Apple will not help you.'

There is no paying service, in the world, that will be able to defeat Activation Lock security feature.

That iPad is dead to you!

Sorry.