It used to be quite a hassle to add 3D models to web pages.
Here are a few resources to get you on your way
This is the 3js documentation
Where possible, we recommend using glTF (GL Transmission Format). Both .GLB and .GLTF versions of the format are well supported. Because glTF is focused on runtime asset delivery, it is compact to transmit and fast to load. Features include meshes, materials, textures, skins, skeletons, morph targets, animations, lights, and cameras.https://threejs.org/docs/#manual/en/introduction/Loading-3D-models
We dig this tutorial by Main at Medium,
It goes over modeling and texturing a bus, then adding it a three.js project
another guide lives here