You must be a beginner because your question lacks a lot of necessary information to really give you an answer.
Making tons of assumptions: You've got a variable that when you look at it shows you a date in a specific datetime format. You want to change this format to something else.
If above is true: SAS stores datetime formats in a numerical variable as the count of seconds since 1/1/1960. You then just need to apply a format to such a numerical variable so it prints this number in a human readable form. The only thing you need to do to in such a case is change the format applied to the variable.
The SAS datetime formats that are available are documented here.
Assuming your locale is set to US below format should work.
/*options locale=en_us;*/
data sample;
dttm_internal_value=datetime();
dttm_formatted=dttm_internal_value;
format dttm_formatted nldatms.;
run;
...and as a semi-serious comment as a non-US person: The cost to the global economy and lives the US causes by still using MM/DD date formats and non-metric systems must be significant.