If you need to view 3D objects in 3DMF files, you'll need an application that can read the 3DMF modeling format.
Surprisingly, such applications are few and far between which is why the developer has created 3DMF Viewer. 3DMF viewer allows you to do much more than just view them though. It enables you to compose 3D worlds with several objects, manipulate objects independently from each other and You want to be able to move them freely around each other. It's pretty much a once stop shop for most 3DMF needs.
You can open individual 3DMF files with an open dialog window or by dropping them on the viewer window because it supports drag and drop. You can also select and manipulate the camera, view and edit the position, orientation and scale of the camera and the objects and save and open the scenes you've created. In addition, you can also set the light settings according to your preferences.
Considering it's free and doesn't require any installation, 3DMF Viewer seems like an excellent tool if all you want to do is view 3DMF files.