A Draco (.drc) file can contain only a single geometry, as far as I know. It’s a very basic format compared to something like FBX or glTF — no animation, no materials, not much else.
I would suggest converting your FBX to glTF (using FBX2glTF or Blender) and then adding Draco compression to the glTF file using glTF-Pipeline. That way you get all the features of glTF, but still have Draco compression on the individual geometries. You could also use https://github.com/zeux/meshoptimizer/tree/master/gltf for a different compression option, depending on what you need.