Sites like Convertio.co or Files-Conversion.com sometimes claim to handle .mscz . I tested these extensively. Most of them are faking it.
If you are a beginner, follow this exact workflow to avoid errors. mscz to midi online converter hot
MIDI is the universal language of digital music. While .mscz holds layout and engraving data, MIDI holds the performance data. The Ultimate Guide to MSCZ to MIDI Online
: You can use the built-in export feature in MuseScore to convert your MSCZ file to MIDI. If you don't have MuseScore installed, you can use their online version. However, this might require you to create an account or install the software. Most of them are faking it