use tempdb
go
create table t (NUMBER int, ITEMCODE varchar(15), FILENAME varchar(15))
insert t
select 1 , 'ITEMCODE1' , 'FILENAME1' union all
select 2 , 'ITEMCODE1' , 'FILENAME2' union all
select 3 , 'ITEMCODE1' , 'FILENAME3' union all
select 4 , 'ITEMCODE2' , 'FILENAME1' union all
select 5 , 'ITEMCODE2' , 'FILENAME2' union all
select 6 , 'ITEMCODE2' , 'FILENAME3' union all
select 7 , 'ITEMCODE2' , 'FILENAME4'

go
create view vw_t as

select ItemCode
       ,[FileName1] as [FileName1]
       ,[FileName2] as [FileName2]
       ,[FileName3] as [FileName3]
       ,[FileName4] as [FileName4]
from   (select number, itemcode, FileName
        from  t) d
PIVOT (max(Number)
FOR [FileName] in (FileName1, FileName2, FileName3, FileName4)
) as p

go

select * from vw_t

go
drop view vw_t
drop table t

OUTPUT:
ItemCode        FileName1   FileName2   FileName3   FileName4
--------------- ----------- ----------- ----------- -----------
ITEMCODE1       1           2           3           NULL
ITEMCODE2       4           5           6           7

SELECT t.ITEMCODE,
MAX(CASE WHEN t.Seq=1 THEN t.FILENAME ELSE NULL END) AS FILENAME1,
MAX(CASE WHEN t.Seq=2 THEN t.FILENAME ELSE NULL END) AS FILENAME2,
MAX(CASE WHEN t.Seq=3 THEN t.FILENAME ELSE NULL END) AS FILENAME3,
MAX(CASE WHEN t.Seq=4 THEN t.FILENAME ELSE NULL END) AS FILENAME4 
FROM 
(SELECT ROW_NUMBER() OVER(PARTITION BY ITEMCODE ORDER BY FILENAME) AS Seq,*
FROM YourTable)t
GROUP BY t.ITEMCODE