How would I go at converting .3DC + .DDS files into .OBJ + .MTL + .TGA?
This is actually very simple to do, this goes for mostly any file format but for this I'll be using .3DC file. Download 3D Object Converter, you'll have to pay a fee if you want the program to completely convert your object without removing every 5th quad or triangle. After you've done that open it and go into the menu and click batch convert. Add your file you want to convert change the options so that they suit you and choose the export for .obj Wavefront don't take any other type of .obj file format. You can find it near the end of the list. Then convert the file. And voila!
If your texture is in dds format or whatever and you want to change it to tga, just use an online picture converter.
After that amend the file.mtl and change to the correct texture it should call to.
And there you go!