@yallneedtherapy You'd need to uninstall the disc version of Sims 3, clean your computer's registry to get rid of the game's leftover traces, and reinstall through the EA App. An uninstaller like Revo can remove the registry entries for you while also removing the game, or you could use Piriform's CCleaner to clean the registry instead. The free version of either app is fine.
If you still have the codes for your base game and packs, and you never registered them, you can do so now within the EA App's game library, and the content will be added to your account, so you don't need to buy it again. If you did register the content, sign into whatever EA account you used at the time, and you should be able to install everything.
