With Finale music notation software users may create new templates (.ftm) based on already existing Finale files, which may include .mus files that store music notation. It is unlikely any other 3rd party software is capable od this type of conversion.
Convert Finale music file format to Finale template file.
We have found one software suitable in our database for this conversion.
Microsoft Windows software - convert mus to ftm on Windows
One of the most popular music notation software on market
Convert from mus file format
The table with program actions contains information about what each program is capable of doing with their files. This may be a good pointer for further searches for certain file conversions and help you find the converter you are looking for if our search result is insufficient for you. However, it is far from perfect and may sometimes show results which are not really usable because of the nature of the software handles the files. So a conversion that appears as possible, just because of matched actions, may in fact not be possible.