Should the files even be in a folder on your USB?
Without knowing the exact steps you took from download to upload...its all a mystery to us. We don't know if you have an FSC code, or if you even powered the car (you didn't mention either). Take the time to give a step by step of the process you did...that's the only way (without throwing question after question at you) as to where you may need to make a correction.
There are also videos all over YouTube on how the steps you need to take once you've downloaded the files to your computer...to formatting the USB drive, to copying the files to the USB drive.
Help us help you better...the more details you give, the closer you'll probably be to having your new maps.
Here's an example of how to upload maps to a USB drive...then upload the maps to your BMW: