Sims 2 pets installing code

Hello,i have recently purchased the Sims 2 pets expansion pack for the PC and when i opened it there was no manuel. And as you probably know you need the code on the back to install the game, witch i did not have. Im dissapointed about that, because now i cant install and play on it. So i was wondering if there is anyway that i can get a code from for the Sims 2 pets so i can install it. Please tell me if there is anything me or you can do about it. I would appriciate it very much.

Thank you