Re: Cannot find games following a hard drive change

@SierraLeone4  You should be able to download and install the base game and expansion and stuff packs from Origin without needing to input a code again.  Just open your Origin library, click on the Sims 3 icon, and then click the Install button.  If Origin doesn't ask you whether you want to install all your packs as well, you can manually start those downloads once the base game is installed.

If you own any store worlds or other store items, you'll need to download those through the store itself.  Go to store.thesims3.com, sign in with your Origin credentials, then click Store > My Store Account > Purchase History to view your owned items, or just download them directly from their product pages.