Can't even find the correct Sims 3 folder

@yauyau63  The EA Games folder holds the game's program files, as in, what the EA App installs.  The Electronic Arts folder inside Program Files holds the program files for the EA App itself and has nothing to do with installed games.

The Sims 3 user folder is still always going to be in Documents > Electronic Arts.  You will need to start the game once in order for the folder to appear.  If you don't see it, check the Documents folder inside OneDrive, or the one that isn't in OneDrive if that's where you looked first.

Thank you for your response. There are no files in my OneDrive, probably because this is a new computer that I specifically bought to play Sims 3.

I have already launched Sims 3 and played for about five hours. However, in my Electronic Arts folder, there are only EA Desktop and VC, and neither contains any Sims 3 files.

@yauyau63  Again, the Electronic Arts folder inside Program Files is completely irrelevant here.  It's only purpose is to hold EA App data.

When the game launches for the first time, it will create a Sims 3 user folder.  It has to in order to load; if it can't write to this folder, the launcher won't even open.  The folder could be deleted after the fact, but if you can load the game and see a previous save, that's not happening either—the folder needs to be present somewhere, containing your save data and a bunch of other files and folders.  There's nowhere else the save could be.

Please open a File Explorer window, click This PC in the left panel, and enter DeviceConfig in the search field in the upper-right corner of the window.  When the seach is finished, click on the result, select "Open file location," and you'll jump to where that file is, which will be inside the Sims 3 user folder.  You'll see the full path in the address bar.

If the game is reading a different location than what you want, for example if it's reading C:\Users\Public\Documents, the next question is what the Documents directory is, as Windows sees it.  For that, search in Windows for Command Prompt, open it, and enter this command:

reg query "HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\Shell Folders" /v "Personal"

Then post the result here.  This location can be changed if necessary; the important point is that Sims 3 will always use this location if it can.