A .cas file is a model, while a .dds one is a texture, completely different things, no conversion from one to the other.
Oh.
Well what i wanted to do was modify a bunch of textures, but i dont know where the folder containing them is at. I have used the vercingetorix unpacker, just to let you know.
Textures are in data/packs/models_unit_textures.pak in vanilla; you'll need to unpack it, modify the textures and then either re-pack or delete/rename the .pak file and move the data/packs/data/models_unit folder inside data/.
Textures are in data/packs/models_unit_textures.pak in vanilla; you'll need to unpack it, modify the textures and then either re-pack or delete/rename the .pak file and move the data/packs/data/models_unit folder inside data/.