Regular Expression to match last six digits in a string : I have a text file that contains roughly a thousand file names that I need to change slightly. Each file name is a date and time formatted like: "2013-05-01 120125.jpg"

I need to convert all of them to: "2013-05-01 12.01.25.jpg"

I'm assuming this would be fairly trivial with regular expressions, but I am always confounded when I try to do anything with them! Help is appreciated!