I converted models created in blender successfully to 3ds. There is a free software available that includes other converters. The software is called WINGS3D. So I was able to export e.g. wavefront *.obj files from blender, open them in WINGS3D and then export them to *.3ds. They work fine in BridgeCommand. WINGS3D also contains an export tool to *.x, which I never tried. WINGS3D is available for WIN, Linux and MAC.