-- Setup
DECLARE @Temp TABLE(Port VARCHAR(3), Reference VARCHAR(7), Status VARCHAR(3), BrokerNumb INT)

INSERT @Temp
SELECT 'POW', 'AJF768P', 'SIM', 999
UNION ALL SELECT 'POW', 'AJF768P', 'FLD', 19 
UNION ALL SELECT 'POW', 'AJF123P', 'SIM', 123 
UNION ALL SELECT 'POW', 'AJF123P', 'FLD', 56 

SELECT *
FROM @Temp

-- Update
UPDATE
	U
SET
	U.BrokerNumb = S.BrokerNumb
FROM
	@Temp AS U
INNER JOIN
	@Temp AS S
	ON U.Port = S.Port
	AND U.Reference = S.Reference
WHERE
	U.Status = 'SIM'
	AND S.Status = 'FLD'

SELECT *
FROM @Temp