Query to change the column Type to another Type

DECLARE @SourceColumn NVARCHAR(MAX),
@DestinationColumn NVARCHAR(MAX)

SET @SourceColumn = 'VARCHAR'
SET @DestinationColumn = 'NVARCHAR'

SELECT
'Alter Table ' + OBJECT_NAME(c.OBJECT_ID) + ' Alter Column ' +
c.name + @DestinationColumn + '(' + CONVERT(NVARCHAR(MAX),c.max_length) + ')'
FROM sys.columns AS c
JOIN sys.types AS t ON c.user_type_id=t.user_type_id
WHERE OBJECT_ID = OBJECT_ID('tb_test')
AND t.NAME = @SourceColumn