mpx to mmap conversion is often searched by users that are looking for a way to use Microsoft Project content (in this particular case MPX export files) in MindManager, in order to use the MS Project data in their mind maps.
We know that MindManager does indeed support import of MPX format, but it's probably not a file conversion, but merely using the content for making new map or adding it to existing one.
You can actually find this topic covered in several YouTube videos, so if you need help with this kind of export, it might be worth your time to watch the videos.
Updated: October 6, 2023