Selenaksantos Your computer absolutely does have a Sims 4 user folder somewhere when the game is open. If there was no folder and it couldn't create a new one, the game would throw and error instead of even starting to load. And since you keep getting notifications for the same mods, it's likely that folder is staying put wherever it is even after you quit.
Where exactly does the game itself say your user folder is? It would be easier for me to have an exact location when describing what to do. In the interim, open a File Explorer window, click This PC in the left panel, double-click the drive the game lists (probably C), and then open the successive folders you see in the game window.
The point is that while your computer has multiple Documents folders, and you may simply have been looking at the wrong one, going through File Explorer and manually opening each correct folder in sequence will get you where you need to go.