The Final Draft extension may have been stripped from the end of the file name.
First, copy the file from the USB drive to your Desktop and work off that one. Rename the file so that it includes the .FDX extension and the program should be able to recognize the file and open it.
A file named (for example) Harry and Sally on the USB drive should be moved or copied to the Desktop and renamed Harry and Sally.fdx.
2022
https://fd.support/43zc684