Both .ms14 and .ms13 files come from NI Multisim circuit design software, albeit from different versions of the software. Unfortunately the software is not backwards compatible, meaning it is not possible to convert newer files to older files. Maybe there is some kind of workaround for this through some exchange format, but direct ms14 to ms13 conversion is simply not doable.
f you need something else with these files, perhaps contacting Multisim support or reaching out to the online community might be of help.
Updated: August 3, 2023