Convert Drupal 7 Theme to Drupal 8?

Hi, I purchased a Drupal theme, not knowing it was made for Drupal 7 and not Drupal 8.

What is the easiest way to convert this theme over to Drupal 8? I’ve read this documentation:

But it does not help me as the core/modules/system/css/system.module.css directory doesn’t even exist and it is hard to believe that making these changes are all you need to do when the whole change with .info to .yml happened as well (amongst many other things I asssume)

Is there a module that will convert it? Like the module to convert a drupal6/7 site to Drupal 8?

Any help is appreciated. Thank you.

Drupal version: