Q: Factory settings

The iPad is on the activation screen ? If you had Settings > iCloud > Find My iPad enabled on it you will have to type in the account id and password to re-activate it - that can't be bypassed, it's activation lock.

Are you still logged into the account anywhere so that you can look it up ? Or do you have any of the account's downloads in your computer's iTunes library so that you can do 'get-info' on them and see the id ? If not have you tried : If you forgot your Apple ID - Apple Support ?

If you still can't remember/find your id, and if you were the original purchaser of the iPad (i.e. it wasn’t bought used) then 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

Hi

Have you had this ipad from new ?

Contact  iforgot.apple.com

Cheers

Brian