You can open .fbx, .bvh, .htr, .trc, .amc, and .c3d files with the File > Motion File Import method.

To open a motion file:

1. Select File > Motion File Import from the MotionBuilder menu bar.

   The Import Files dialog box appears.

   

   Import Files dialog box

2. Navigate via the Import Files dialog, and select the file to import.
3. Click Open.

   The Import Options dialog box appears.

   

   Import Options dialog box

4. Disable any elements of the file you do not want to load with the file.
5. Click Import.

   The file loads in MotionBuilder.