Hi,
have a look at the documentation : https://docs.mendix.com/refguide/parse-and-format-date-function-calls
what you are looking for is ‘MMM’ .
formatDateTime($dateTime, ‘MMM’)
an overview of simple date formats can be found here: https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/text/SimpleDateFormat.html