Bekahboo1023 You don't need to register your codes a second time. They should already be attached to your original account, and you can simply login to that account and download the content.
If your content isn't in your account, or you can't find the account you used the first time around, you'll need to contact EA customer support. First, take a photo for each pack showing the disc, its case, and the product code (clearly readable). You can upload these when you submit the help request.
I would strongly suggest using the live chat option rather than email. If you don't see it, try this link:
https://help.ea.com/en/help-contact-us/?product=the-sims-3&topic=missing-game&category=manage-my-account&subcategory=find-missing-game
Make sure you're signed into an EA site (this one is fine) before clicking the link and that the location in the lower-right corner of the browser window is set to U.S. or U.K.
Alternately, try using the help site without being signed in. Some categories of issue allow you to proceed without an active login, and many of those offer the live chat option.