Finale NotePad can open and convert the 2005 .mus file format if NotePad’s version is 2005 or later.

NotePad will convert to the NotePad version’s file format.

Thank you but I am unclear what Notepad would convert "to" -- I don't know what you mean by "Notepad version's file format." Is it MusicXML? 

If this is to be believed, you can still download NotePad 2012 for Windows, open your old .mus files and export as MusicXML. 2012 was the last version released IIRC.

https://www.finalemusic.com/products/notepad/

I'll try that; thank you.

Here’s the manual online.

https://usermanuals.finalemusic.com/NotePad2012Mac/Content/NotePad/Reference.htm

For MusicXML import/export, you will need to download and install a Java runtime library from Oracle if you don’t have one installed already. The correct one will be 32 bit comparable.

Just don't clear your thumb drive until you are sure the converted files successfully represent what you started with.

Thanks again. While I'm able to use a computer reasonably well, I'm not savvy on such things as a Java runtime library. It is something I download and install, and it is plug-and play, or I have to educate myself?

I won't be clearing the thumb drive; it is my storage medium and the only other thing I can think of would be to write a few CDs. I'm unhappy with electronic storage in general because all of it can disappear; I want my music in print ... which I supposed can still get burned up but it won't suffer from a failed electronic storage medium.

Cool....it worked right off the bat. Thank you!