Insert space between numbers and text

I have a list of sizes where the format is number and then text unit of measure--the number always comes first. If there is no space between the numbers and the letters I need to insert a single space. The number can be of varying length. The list is several hundred rows. Can a formula be written to do this? I've uploaded a small sample file that should pretty clearly illustrate what I am trying to do. Thanks for any help!