There probably is a better way to rescue them, but to address your question...

I suggest copying the file(s) to a different location as a backup in case whatever program you use to read it corrupts the file.

What is the extension of the file name, if any?

By default, Windows hides most file extensions from you. To work with files as accurately as possible, I suggest unhiding them. This Microsoft support article has the steps: http://support.microsoft.com/kb/865219.

The file only says file type is "file".

I have spent 3 days on this now and I'm fed up. I think I'll try using some email recovery software.

Thank you for your help.

how about keeping it all in one thread..... I nominate this one https://support.mozilla.org/en-US/questions/990235

Forgive my faux pas----I am a novice.