Where is the Sims 3 registration code when you download the game from origin?

log into your origin account right click the game icon-show game details your code should be there if your still logged into origin log out log back in to refresh/reload the game ...is the serial code 16 digits long thay might be for a dlc content item you can try to redeem that on your the sims 3 account to see if it was/is a dlc item the game code should be 20 digits long to see if the 16 digit code is for a dlc item try this here  http://www.thesims3.com/incentive/generalredeem

1. Follow the instructions on redemption on the page.
2. Go to your purchase history to download the set