The whole folder \js is gone. The latest release, that contains this folder is r147. Newer releases contain '\jsm`. So you have three options:
switch to a newer Three.js (which uses modules, so this renderer is in the \jsm folder).
switch to an old Three.js (that has \js folder).
pick the new renderer (jsm version) and convert it into non-module (js version).
Whatever option you choose, you still have to include CSS3DRenderer.js separately, because it is an addon and it is not part of the main Three.js file.