Help me in converting SQL to PQL

I would like to identify the incidents for which the assignment group is changed more than two times. I am able to write this in SQL but need some help in converting this to PQL

SELECT INCIDENT_NUMBER,COUNT(*)

FROM "_CEL_INC_ACTIVITIES"

WHERE ACTIVITY_EN = 'Change Assignment Group'

GROUP BY   INCIDENT_NUMBER

ORDER BY 2 DESC

Thanks in Advance