The "moneydance jan 24 10.md-2011-08-29" file looks to be a backup file for an older version of Moneydance.
You have two options...
A) You can download the version of Moneydance that you used to create that file and then rename "moneydance jan 24 10.md-2011-08-29" to "moneydance jan 24 10.md by removing the -2011-08-29. You should then be able to open the file using that version of Moneydance. https://infinitekind.com/previous-versions-of-moneydance
B) You can rename "moneydance jan 24 10.md-2011-08-29" to "moneydance jan 24 10.md by removing the -2011-08-29. Doing should allow newer versions of Moneydance to convert the older version to the newer format.
From reading your post, it sounds like you may have already installed a newer version of Moneydance so...
Back up / make a copy of your original file, (moneydance jan 24 10.md-2011-08-29) then rename the file as suggested above, then try opening it with the newer version.
Ethan on 27 Sep, 2021 12:27 AM
Just to add to Kevin's excellent information above: If you rename and open that file using a newer version of the program (by using the open other option from the Moneydance welcome screen or the menu bar [File -> Open -> Open Other]), the program will convert the .md data file to the newer .moneydance file format. There's no way to actually update the .md data file that you have now in a newer version, but you can edit all that data after it has been converted into that .moneydance format. I mention this mostly so you don't make any changes and think they're being saved in the .md file.
If you do want to try Kevin's method A instead, I recommend using Moneydance 2011, which was the last version that used the .md format, and should be able to open any .md file made in a previous version. That also seems consistent with the 'date' at the end of your backup file name.