In column F Ive got a list of skus which look similar to this - DEC-RAINB-0916-1

At the end of every one is a number from 1 to 50. I want to make it so that the single numbers (ie 1-9 still have two numbers so 01, 02, 03). Obviously if I do a simple find and replace it will mess up the two figure numbers too (ie find 1 and replace with 01 will also change the number 10 to 010). Is there an easy way around this?