The converter does not exist on Mac. As simple as that. A simple reason for that is maybe that Vue does exist on Mac only since version 4. So the situation is a little tricky I fear. I think you need to install Vue 4 on a PC, open the files there and save them then in Vue 4. THEN you can copy them over to the Mac and use them there. If that is not possible (not all have a PC at hand) then you should contact the creators and ask wether they can do it for you - or allow that a friend does the conversion on PC for you.

One day your ship comes in - but you're at the airport.