There is not much you can do from the iPad. You'll need to use a computer browser to access me.com, go through the junk mail folder and move it back to the inbox. Don't forget to mark it as not-junk.
Also, adding the from email address to your me.com contacts should prevent MobileMe from placing those emails in the junk mail folder in the future.
It is technically possible to visit me.com using third party browsers like iCab Mobile and Atomic, and changing their browser ID; however me.com does not work properly with any iPad browser, and it is difficult if not impossible to get anything done that way.