Ok look, I'm not so good with map making but i do know this,
-When you go to save a map and in it's location you chose to save it to, will have the .mis and the .ter of the map
-The .mis is the lighting of the map (i think)
-The .ter is the terrain of the map (without this you will have outer-space :/)
Now your question with the converting- I have no idea...