SELECT ComCod    = MIN(COMCOD)
,       PartyCode = MIN(PartyCode)
,       PartyName
   FROM dbo.YourTable
  GROUP BY PartyName
  ORDER BY PartyName
;

if object_id('tempdb..#TestTable') is not null
    drop table #TestTable;

create table #TestTable (
    COMCOD nchar(4),
    PARTYCODE nchar(6) PRIMARY KEY,
    PARTYNAME nvarchar(250));

insert into #TestTable
values
('3305','100028','Premier Cement Mills Ltd.'),
('3305','100029','Premier Cement Mills Ltd.'),
('3305','100030','Premier Cement Mills Ltd.'),
('3305','100031','Premier Cement Mills Ltd.'),
('3305','100032','Premier Cement Mills Ltd.'),
('3305','100033','Electro Power Engineering Ltd.'),
('3305','100034','Electro Power Engineering Ltd.'),
('3305','100035','Electro Power Engineering Ltd.'),
('3305','100036','Electro Power Engineering Ltd.'),
('3305','100037','Islam Trading Consortium Ltd.'),
('3305','100038','Islam Trading Consortium Ltd.'),
('3305','100039','Islam Trading Consortium Ltd.'),
('3305','100040','Mr. Ehsanur Rahman'),
('3305','100041','Mr. Ehsanur Rahman');

with BaseData as (
select
    COMCOD,
    PARTYCODE,
    PARTYNAME,
    RN = ROW_NUMBER() over (partition by COMCOD, PARTYNAME order by PARTYCODE asc)
from
    #TestTAble
)
select
    COMCOD,
    PARTYCODE,
    PARTYNAME
from
    BaseData
where
    RN = 1
order by
    COMCOD,
    PARTYCODE;

if object_id('tempdb..#TestTable') is not null
    drop table #TestTable;
GO