Please disregard previous reply.
The reason you can't find your USB device is that you're looking at the internal storage there!
If you're in the kitchen and looking for your bed, it won't work until you leave the kitchen, enter a hallway/stairs and enter a different room.
Click parent directory until you see something like SDA1 and click it. That'll be your USB device.
If you don't see SDA1 after pressing Parent Directory a lot, then click on the MNT folder you'll see if you've gone to the root. Look for SDA1 there. No joy? Press Parent Directory and look for the STORAGE folder and click it, again look for SDA1 or similarly-named folder and click it.