Q: How can I get my registration number

Please explain. Registration number for what? Apple doesn't use anything other than a serial numbler for checking computer ownership or support status.

Also please tell us what Apple equipemnt you are inquiring about so we can get you moved to an active forum. This one is for Apple products made before 1998 and gets almost no views, and I doubt you are asking about that old a device

No one will see your post here--that's why our getting enough info from you to ask for a move is important to your getting fast help.