Add prefix to link url

Based on this question about retrieving WordPress post slug, you could put together a link like the following:

<a href="http://www.example.com/md/<?php global $post; echo $post->post_name; ?>">link text</a>

Whether that goes to a functioning page or not, I don’t know. It seems like you may want to change rewrite rules in the functions but I’m not sure from what you’ve said.

By the way, you may want to read why links that only say ‘Click here’ are bad practice for SEO and accessibility.