Concatenating Multiple Rows into single row

SELECT customer_product_id,
SUBSTR(MAX(REPLACE(SYS_CONNECT_BY_PATH(incident_number, '/') ,
'/',' ,')),3) Concatenated_String
FROM (SELECT cia.incident_number,cia.customer_product_id
,ROW_NUMBER () OVER (PARTITION BY customer_product_id ORDER BY customer_product_id) row#
FROM cs_incidents_all cia
,csi_item_instances cii
WHERE 1 = 1
AND cia.customer_product_id = cii.instance_id
AND cii.serial_number = 'XXXXXX'
AND NOT EXISTS (
SELECT 1
FROM cs_incident_statuses
WHERE NAME IN ('Cancelled', 'Closed')
AND incident_subtype = 'INC'
AND incident_status_id = cia.incident_status_id))
START
WITH ROW#=1
CONNECT
BY PRIOR row# = row#-1 and prior customer_product_id = customer_product_id
GROUP
BY customer_product_id