Hi @CassMay If there is another "The Sims 3" folder on your computer, you should be able to find it by doing a search for that file name. I've been searching file names in Windows 10 by just opening up File Explorer and typing in the name in the search box at the top right. If you have two folders, you can check the dates/times on both folders to have an idea of what your game is using. Take a look at where that second file is located also. You can also check to see if your saved games and recent downloads are in the second folder that's presumably in a different place just by looking in the Saves and Downloads folders.
If so, then you would obviously need to do some combining/moving to get everything in the right place. I may not be the best person to address the easiest/best way to accomplish it, but I'm sure someone else better equipped to handle it will be along shortly to help out.
If you don't find a second The Sims 3 documents folder on your computer, open your launcher and go to installed content and make sure the run without custom content box there isn't ticked.
If neither of those two things are the problem, then you probably either did do something wrong with your mods folder setup, even though you think not :) (it's happened to me even when it wasn't my first try), or you didn't install the cc files properly. There's a link above in the thread re. the different file types and how to handle them.
Since this is an "older" thread, it may get closed out before your problem is completely solved (although since there's been some ongoing, helpful discussion in it, it also may not). If you can't post again here regarding this problem or if you have another problem while you still have new member status on the forums, here is a link to a thread for new members to post about problems they're having:
https://forums.thesims.com/en_us/discussion/893122/thread-for-new-members-to-post-their-sims-3-game-issues/p1