As you probably know if using CodePlex, it will shutdown by the end of 2017. The option suggested by CodePlex is to move to GitHub.
Click to Read More
The move is facilitated by an automated "import" procedure. But HTML pages created on CodePlex are not automatically converted into Markdow.
This can fortunately be done using Pandoc.
For demo purpose, pick From = "HTML" and To = "Markdown (GitHub)".