Audacity-projects consist of two parts : a small “.aup” file and a big “data” folder.
The file without the folder is useless : the small “.aup” file does not contain any audio.
Moving Audacity projects is a tricky business, see …
https ://manual.audacityteam.org/man/audacity_projects.html#move
Also recording to an external drive, rather than the local one, is risky