Thank you. We have already done all the items on that documentation that are available for Moodle 3.3. I suppose we can upgrade to 3.4 to try the new HTTPS conversion tool but we aren't quite ready for another update yet.
The information in the sidebar of the document you sent seems to be about password authentication and general security, not HTTPS. Am I misunderstanding you?
Our students are not reporting difficulty accessing the site. They just don't like to see that warning in google chrome and firefox (in the address bar) about not secure images. So I was wondering how to find the images causing the problem since we already ran the DB search and replace tool.