Better to convert you files in Obj format then import to Moi

3 methods
Only the Structure
http://moi3d.com/download/Obj23dmWireframe.zip (a program) by Michael Gibson
File will be converted in format 3dm

By native Subdivision - Menu SUbD / Create/ From a File
File will be directly subdivided and converted in nurbs

By Plugin By Max Smirnov _ImportOBJ
Original Structure to Subdivide
File will be imported nd converted in nurbs and will be parameter for be subdivided a
http://moi.maxsm.net/files/scripts/ImportObj.v.1.5.2015.09.10.zip

In any case better to have quadrangulated surfaces and a max reasonable polys number of 150 000

So use free MeshLab (can convert your files Stl or Fbx too) or Instant Meshes for this quadrangulation!
https://www.meshlab.net
https://github.com/wjakob/instant-meshes