@JennaStaAna2005 Okay, so then there are two ways you can go. You can delete the files off the USB, cancel the repair, clear Origin's cache, and restart your computer. Then you can open Origin, right-click on the Sims 4 icon, select Move Game, and choose the folder that you created on your USB as the destination. You wouldn't move any files yourself, you'd let Origin do it for you.
The other possibility is that you clear Origin's cache, delete the files off your main hard drive and leave them on the USB, and restart. Then you go into Origin, right-click on the Sims 4 icon, and select Locate Game. From there you'd select the game on your USB, and Origin should verify the install. It's still a good idea to repair, then update.
If the Locate Game function doesn't work, clear Origin's cache, restart your computer, open Origin, and click Download on the Sims 4 icon. When it asks you where you'd like to download the game, choose the location on the USB. Origin should start the download but then verify the existing files instead of downloading them fresh.
Any of these approaches can work, and they all do work at least a lot of the time. If one doesn't, just try something else.