Looks like you are using a REGEX formula or tool. And I guess the three columns you want to separate a date into is the day, month and year. I assume the date is already formatted and recognised as a date.
In that case, I would not use REGEX. I would use the formula tool and use the following built-in functions:
DateTimeDay([FieldName])
DateTimeMonth([FieldName])
DateTimeYear([FieldName])
If the date you have is not yet formatted or recognised as a date, you can add a step to parse/format as a date first, then do the above. I should note, you could use REGEX and that would work also - more than one solution here, matter of preference.
