I can' t find the registration number.

Apple wrote:

If you do not have the retail box or envelope or cannot find the card or booklet inside, contact AppleCare Agreement Support with your original receipt (or purchase order) and the serial number of the product covered by the agreement.

i have the apple care protection plan booklet that i have bought with my new mac, however i can't find the registration number inside

Enter the serial number of your iPad here:

https://selfsolve.apple.com/agreementWarrantyDynamic.do

What does it say about your warranty status?