Hi elizabethfromnew market.
Re: The folder is empty.
Wondering if the USB drive is formatted to be compatible with MacOS.
(The files may be there yet if the drive is not compatible, no files can be transferred.)
Here's Apple Support's article:
Connect and use other storage devices with Mac – Apple Support
(NB: says a USB Drive needs to be properly "ejected" after use.)
File system formats available in Disk Utility on Mac – Apple Support
How to: Erase and reformat a storage device in Disk Utility on Mac – Apple Support
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Re: Is there anyway to recover these files?
Eg: If they happen to be Windows files on a drive formatted for PC,
the files would likely be available on a PC.
Otherwise, sorry. I don't know of a way.
(There are commercial data recovery services but have no experience with those.)
All the best :-)