35100 Mod Re-Write 301 redirect

I have a site on an apache server with mysql and I recently changed all the url's from underscores to "hyphens". Now I need a 301 redirect to redirect all the _names to -names in the url so I do not lose all the search placement. This project is for an .htaccess mod-rewrite fix for the site. Here is the exact format [login to view URL] [login to view URL] They need to go to this format: [login to view URL] [login to view URL] This should be a piece of cake for anyone who has ever done one :)