To reiterate @Centaur.
The OBJ/MTL file combo will not work because the OBJ file is written to look for an MTL file named ‘Daikenki.mtl’
The MTL file supplied with ‘P2_Samurott.obj’ uses the same name as the OBJ itself !
If you rename the MTL file to ‘Daikenki.mtl’’, then it will find it.
However, since the MTL file is itself looking for image files in ‘Textures…’ etc, it will not find them - because the JPG files are currently supplied in the same folder as the OBJ/MTL files.
You can fix this by copying those two JPG files into a new subfolder named ‘Textures’…
If that works we then know that at least the OBJ/MTL work as they should.
Because the 3DS file is binary encoded, it’s harder to see what images [if any] it might be looking for.
Perhaps having the JPG files in ‘Textures’ will work ?