Sims 3 code already redeemed

@MoonhunterZ  If your codes have already been used, likely by the original owner, then there's nothing you can do to add the games to your Origin account.  Codes can't be transferred from one account to another, nor can they be removed once they've been registered.

Technically, you might be able to install the game via disc and leave Origin out of it entirely.  But if your base game disc requires you to use Origin to install, then you're unfortunately out of luck.