Activation Lock
How do I get rid of the activation lock? I don’t know the apple id
iPad mini 3 Wi-Fi, Cell TD-LTE
If you can't remember your id have you tried : If you forgot your Apple ID - Apple Support ?
Or, and if you were the original purchaser of the iPad (i.e. it’s not second-hand), you could try going to an Apple Store (make a Genius Bar appointment if you do) or try contacting iTunes Support online (https://www.apple.com/emea/support/itunes/contact.html) and see if they can remove the iPad from the account - they are likely to want to see proof of ownership before they might help e.g. original receipt with the serial number on it
If you bought the iPad second-hand contact the person you bought it from