What type of file better

I have an model of building and terrain in 3DMAX. On this model a lot of trees, so output file is large. What settings and file type better to load in this situation?

The recommended format for importing objects in Three.js is glTF. See here: https://threejs.org/docs/#manual/en/introduction/Loading-3D-models

You can preview how (and if) your model will import with this tool: https://gltf-viewer.donmccurdy.com/

I’m not familiar with 3DMax so it’s difficult to recommend settings. But if you have objects like trees that have the same geometry and repeat in your scene, I think you are better off importing them individually and then cloning them in three.js

Usually for trees, instancing can come very handy too: https://threejs.org/examples/?q=ins#webgl_instancing_modified