how do I unlock my ipad

What do you mean by "unlock"?

-- iCloud: Activation Lock -

http://support.apple.com/kb/PH13695

- This is a security feature so only legitimate (i.e., not stolen) redistribution of devices is possible. See: Turn off Find My iPhone Activation Lock -

https://support.apple.com/HT201441

- If an activation lock was put on a device, only the owner of the account that applied the lock can remove it. Get them to remove it or return the item for a refund.

- Device lock: If you forgot the passcode for your iPhone, iPad, or iPod touch, or your device is disabled - https://support.apple.com/HT204306