rebecca-simone EA doesn't have a cloud saving feature for Sims 3. Saves and all other user files are stored in Documents > Electronic Arts > The Sims 3; deleting this folder is often called a factory reset because it restores the default no-user-content state. Opening the launcher will create a new folder with none of your previous content.
If you can't delete this folder, or you delete it but it returns AND includes your old saves, it's probably a OneDrive issue. The fact that you can't make fresh saves sounds OneDrive-related as well. So unless you have a specific reason to keep it, I would suggest getting rid of it. How to do so is covered here:
📓[GUIDE] [PC] Managing OneDrive | EA Forums - 12636625
The guide was written with Sims 4 in mind but applies equally to Sims 3. Feel free to ask further questions about the process.