How to change format date

[padders]

If date was held in a VARCHAR2 / CHAR column in format DD/MM/YYYY (which incidentally is a VERY BAD IDEA) then you could convert it (on the fly) to a DATE using TO_DATE and the stored format and then TO_CHAR the result using the desired display format, e.g.

TO_CHAR (TO_DATE (string_column, 'DD/MM/YYYY'), 'MM/DD/YYYY')