Microsoft Visio uses both .vsdm to .vsdx files, so vsdm to vsdx conversion represents merely re-saving drawings between different variants, in this particular case from macro-enabled format to the default one.
The best (and only) tool for such conversion is Visio itself and while you can find tool that support import of Visio files, saving to Visio format is very rare.
Updated: October 9, 2023