Hi @saw_isk,
To add on to what @JamesSekcienski said, if you're looking to export student contributions to a discussion, there are no built-in features in Canvas to do that (likely for security/copyright and similar reasons, but I don't know that for sure). The best you'd be able to do to get student posts saved somewhere else is copy/paste, printing the discussion page, or possible having a programmer come up with a Canvas API script to do some of the work for you (but there could be all kinds of edge cases where this would be problematic, like images, videos, other embedded content, just to name a few...).
-Chris