Вы должны использовать ROW_NUMBER и использовать его для генерации столбцов Charge1, Charge2, Charge3 .....
WITH Cases
AS (
SELECT [FileNum]
,[EventCode]
,[ChargeDescrip]
,ROW_NUMBER() OVER (
PARTITION BY [FileNum] ORDER BY [FileNum] ASC
) 'RN'
FROM SourceTbl
)
SELECT [FileNum]
,[EventCode]
,[1] Charge1
,[2] Charge2
,[3] Charge3
FROM Cases
pivot(max([ChargeDescrip]) FOR [RN] IN (
[1]
,[2]
,[3]
)) p