Need to add leading zeroes to string representing a date
My first recommendation would be to use a DATE column type as it is best practices.
If that isn't possible, you can convert the string into a date, then put that in the format you need:
SELECT
  TO_CHAR(TO_DATE(Column,'MM/DD/YY'),'MM/DD/YY') /* I would recommend ISO standard YYYY-MM-DD so the column will sort properly) */
FROM
  /* etc */