what is the question?
generally you would build that in blender, not threejs. even if you don’t know it, the time it takes you to learn basics will be less than trying to make this with a thousand cubes and spheres, and it will look better, too.
More complex 3D objects than primitives like spheres and boxes are modeled in programs like Blender. If you then want to do something interactively in it, then threejs comes up. Then you have to import your 3D models that you created in blender into threejs and then start programming. But if modeling is your primary concern, then Blender is definitely the tool for you