You can export fbx not import fbx with Moi

You can try convert fbx in OBJ format by the free Mesh Lab https://www.meshlab.net
then by Native Moi function SUBDiv / Create from file import this OBJ File
or By _importOBJ by Max Smirnov http://moi.maxsm.net/files/scripts/ImportObj.v.1.5.2015.09.10.zip
Better if your obj file is quadrangulated
maybe something like free Instant meshes can do this quadrangulate (more easy than meshLab)
https://github.com/wjakob/instant-meshes