How do I find my verification code for online purchases?

also please take note the layout of the games has changed in Origin

  http://answers.ea.com/t5/The-Sims-3/FAQ-New-Origin-Layout-for-The-Sims-3-Expansion-Packs/m-p/4641393#U4641393

in your origin that you download to your computer then log in there with the email and password used for the account from the my games tab right click the game icon-download IF it asks for the game code during installation in the my games tab hover the mouse over the icon then click on the i on that a window should pop open with the code on it or right click the game icon-view game details click on that a window should pop open with the code on it