Well, you'll need to group it. And good luck doing that with the delaunay triangles Marvelous Designer exports ;). You're better off using it as dynamic rather than a conformer. If you want to use it as a conformer you'll probably have to retopologize it. In the cloth room (dynamics) those triangle arrangements work in your favor ;).

.obj is the correct format to use, in both cases (dynamic or conformer).

Laurie