I bought an iPad from some one now I want to unlock the activation lock

You have run into the security feature of your device (iPad) and it has executed the Activation Lock. To remove the Activation Lock, you will need the previous owner's Apple ID credentials. Without that information, your iPad will be useless to you. Contact the seller / previous owner of that iPad and get this resolved.

Axel F.

They have to do it. Ask them. Or get a refund.