Convert pmx to x

What is the difference between .pmx and .x?

Description: PMX is a 3D model file format for the MikuMikuDance (MMD) animation software. It is used to store 3D mesh data, bone data, and other information necessary to animate and render 3D models in the MMD application. The PMX format is a binary file which can be either exported from or imported into MMD.; X is a DirectX Model image file used by DirectX technology which is for 3D graphics rendering in games. The file format specifies 3D object structures for meshes, textures, animations, and objects.