MuseScore
MuseScore is currently wining the music score editor race hands-down. And it is Open Source, so no more costly licences, since it is free! If you haven't installed it yet, go to https://musescore.org.
MuseScore can import a variety of music files, and export them as a different type of file, e.g. you can manually load in a musicxml file and then export it as a MuseScore mscz file. An mscz-file is a compressed XML file, but with a far richer set of style definitions than musicxml, BTW. When you have a have a couple hundred of these files that need to be converted, doing this manually on a one-by-one basis becomes tedious. Luckily, It is possible to batch process many files by using a JSON conversion jobfile that lists all the required conversions, and then invoking MuseScore with the -j parameter from the command line. The command is:
mscore -j conversion-job.json
Or, if you are running MuseScore as an AppImage:
/opt/MuseScore-Studio-4.7.0.260513133-x86_64.AppImage -j conversion-job.json
The content of the JSON jobfile is very simple: