How do I create a single score in Musescore? from MuseData

Hi,
I have found a copy of the score for Beethoven's Ninth here
http://www.musedata.org/cgi-bin/mddata?composer=beet&edition=bh&genre=s…

It is in Musedata format. I can open the zip and in folder ..stage2\03 is the third movement. It is a numbered set of files with no extensions.

How do I create a single score in Musescore?

I can see that the files are numbered 1 -20 each being a instrument of group of instruments on the score.

If I rename a file say 01.md and import it I get the single part. Do I have to do that 20 times them assemble them. Is there a way to take 20 parts and create a single score?

Now I need help please.

Thanks for your help in advance.

Dick