extracted the cpk folder, so I found the images in the format "GTX" and has succeeded in the convert "DDS" only worry how to convert again GTX (GFX2) ?
You can import and export GTX textures with TexConv2, you just need to know the right settings, right now it's a big pain to try to do anything tho and TexConv2 is from the SDK so it's kinda illegal but we haven't got anything better yet