How to convert .mdx to .3ds?

I am currently using blender and I can't afford 3d Studio Max currently. I need to open a model in blender that is a .mdx file format. I was wondering if there is a a program out there for download (freeware or free trial) that does that. It doesn't have to be .3ds, it can be any of the Blender importing files which are: .3ds .ac .dxf .dwg .dae .off .x .lwo .mot .md2 .ms3d .txt .c3d .bvh .flt .slp .raw .ply .edl .obj .x3d .wrl. I am a noob to blender, so I don't know if there is a way to do it otherwise. Thanks so much for your help!