I already did
npm install --global webpack
npm install --global webpack-cli
im not sure im reading this right, but in modern environments (webpack et al) you don’t mess with script tags, and usually you don’t touch html files. index.html is an entry point, mostly auto-generated.
your code lives in index.js, you can import from three from there (if you have npm installed it).
i would suggest you start with codesandbox: https://codesandbox.io/s/vanilla
it gives you a proper dev env, you can run code right there, no installation, and if you’re happy just click on download and it zips up a ready-made dev environment (using parcel, which is similar to webpack).