The examples/js folder is gone since r148. This is a step towards a modern and a better manageable Three.js ecosystem. Using OrbitControls.js from examples/jsm in a non-module project will not work as it is. My suggestion is to upload OrbitControls.js to Demoduler and it will try to convert it to the non-module version, that you can use.
Just for reference, it is frowned upon to import resources directly from the three.js domain and you should refrain from doing so, consider using a cdn such as cdnjs.com or hosting a local copy of the required files on your server!
You can find all previous releases of three on their github page, you could download the required files and serve as suggested above…
agreed, lesson learned. among the nearly 10 external libraries I used, OrbitControls.js is the only one I could not find on cdnjs/jsdelivr and alike. I thought the upstream website would be a more stable provider, but it turned out I was wrong.
I have extracted the js/OrbitControls.js from previous releases and uploaded to my site, problem solved. thanks