I think that any work you do in blender should be exported as a GTLF file because that’s the easiest for threeJS to import.
(GTLF is actually two files inside a folder, but something even easier is a .glb because that’s only one file). I recommend you start by trying to export a .glb file from blender.
You will also need to install the GTLF extension, or “AddOn” in blender.
Instructions here: https://www.youtube.com/watch?v=LzdoUTvAgXk
Once your GLTF addOn/extension is installed, follow the instructions here: A Step-by-Step Guide to Exporting glTF Files From Blender - IconScout Blogs
I deleted all the lights and cameras in my blender file (after saving a backup copy) because I will add those back into the scene using threeJS later. Note that this will make the thing invisible (or black) when you open it up using 3D image viewing software. Remember to add back in this “sun” light source, once its in threeJS. In blender its called “sun”, but in threeJS, we call it THREE.HemisphereLight:
This is what the .glb file looks like after export.
If I export and open it using 3D viewer, I can see it because I didn’t delete all the lights and cameras in this case.
But, if I deleted all the lights and cameras, I see nothing.
These are the files inside the folder I named “gltf” with the GLTFs because I exported the blender file twice - once as a .glb and once as a gltf.
About GLTF files: glTF - Wikipedia
Then, your dev can just follow process to add a GLTFLoader into threeJS: Render a custom glb from blender
Diff between .obj and gltf: three.js manual