how to concat one column and multiple values together?

Summary:

I have one query which returns all benefit plans under one employee now i want to fetch all dependent plans name in single row which will be comma separated how to get this? in query want to concat PL.NAME Field

Content (please ensure you mask any confidential information):

SELECT rel_papf.person_number DEPENDENT_PERSON_NUMBER,
ppnf.display_name DEPENDENT_NAME,
'DOB is missing' DEPENDENT_DOB,
papf.person_number ASSOCIATE_NUMBER,
(SELECT NAMEFROM HR_ORGANIZATION_UNITS_F_TL haouf
WHERE organization_id = ASSIGN.business_unit_id
AND TRUNC(SYSDATE) BETWEEN haouf.effective_start_date AND haouf.effective_end_date