Registration for Sims 3 Pets for Nintendo DS3D/xl.

Where is the code at to register this game? I have looked in the manual, case and game disc but I do not see a code to register on the web site. I bought the Sims 3 Pets for Nintendo DS3D XL. It is very small. Do I register this game? I tried at the Nintendo site, but this game can not be registered with them. How do get a warranty on this game if I cannot register it? Also, this is so annoying that I can not just email you, like we use to.