Step 3: Wait. This may take a while depending on how large your Documents folder is and the speed of both the drive you’re copying from and copying to. It took about 35 minutes for me.
Step 4: Now you’re almost done. Once your certain that everything you need has been copied to the new Documents location on the new drive, go back to the old directory of C:\Users\*yourusername*\Documents and delete the old Documents folder as you no longer need it.
Step 5: Start up the Sims 4 and make sure it is loading all of your custom content and mods and tray files, etc. If it is, then you’re done. If it isn’t, make sure you enabled mods and custom content in the Game Options menu. You’ll need to restart the game after checking the boxes if you haven’t enabled them yet. Otherwise, move on to step 6.
Step 6: If something went wrong when copying your files from the old Documents location to the new one, right-click on the Documents icon like you did before and select Properties. Now go to the Location tab and click on the Restore Default button. That should restore everything back to the way it was.