Why can't I access files when I plug my Moto Z into PC?

I'm trying to add & remove videos & pictures from my Moto Z Force to/ from my Win10 PC. When I plug the phone into the USB port it shows up like a normal device like an ext. hard-drive. (it shows XT1650. is there a way to change that to a custom name?) But when I click on it there is nothing inside, no folders or anything. I recently did the same thing with my Kindle Fire & it was super easy. I plugged it in & saw the internal files then I could easily transfer videos to & from it.
Thanks!

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