I'm not sure what the # are for so I omitted them:
Start Date: Left([IW73 TBL with SN]![Start Date],4) & "/" & Mid([IW73 TBL with SN]![Start Date], 5,2) & "/" & Right([IW73 TBL with SN]![Start Date],2)
You can only use Format() on a VALID date field since yyyymmdd is not a valid date field, Format() will not work.