How did you create your project? If you used create-react-app it’s a little tricky to get your assets. If they’re set up properly you should be able to bring up the images via a URL, like http:/localhost/assets/textures/medow_nz.jpg
An alternative is to import URLs, like this:
import px from “…/assets/sky/skybox_px.jpg”;
import py from “…/assets/sky/skybox_py.jpg”;
import pz from “…/assets/sky/skybox_pz.jpg”;
import nx from “…/assets/sky/skybox_nx.jpg”;
import ny from “…/assets/sky/skybox_ny.jpg”;
import nz from “…/assets/sky/skybox_nz.jpg”;