Customizing SharePoint Online Search

Can anyone guide me to a step by step guide on creating new Item Display templates for search results? I have done multiple searches which all lead back to the Master Page Gallery/Display Templates/Search. All the guides show .html documents and .js documents in this location. My location has no .html files, only .js. HOW do I edit what is show as part of an item result? I am lost or I am missing something.  Any help would be appreciated.

Thank you.