Troubleshooting HTML to Markdown Conversion for Search Sources

We have a drive folder that includes a bunch of raw html pages. I am trying to give it to an agent as a "search" source or as an "include data" source but in both instances it seems to be unable to retrieve any information from these sources. Is it because they are htmls? Do we have to convert them to markdown? For context, it's a documentation that's behind a log-in screen so we cannot include it as a website source, hence this workaround