Hi shaalini.
Can u try with the following query

DECLARE @MaxRecId as INT
SELECT @MaxRecId = MAX(RecId )
FROM Rec


SET IDENTITY_INSERT Rec ON
INSERT INTO Rec (RecId,[Name],Description)
SELECT RecId = RecId + @MaxRecId ,
[Name] = [Name],
Description= Description,
FROM Rec
SET IDENTITY_INSERT Rec OFF

INSERT INTO RecItem(RecId,ItemId)
SELECT RecId = RecId + @MaxRecId ,
ItemId= ItemId
FROM RecItem