If you download the models from the tf3dm site, you need to open them with
blender
3dsmax
sketchup
c4d
maya
if you're lucky, the texture is unique then you simply have to export them in directx but if the textures are more, then you have to redo the texture and apply it to the model.
Forgive my english
The software I use? ... Autocad, sketchup, Spazio3D, pconplanner, Kerkythea, wing3d, paint.net.