Conversion from 'uniqueidentifier' to 'int' is not supported on the connected database server

First Change Data Type to any other supported Type like varbinary or anything. then you can convert from that to what you want.

You have to add a new column ( ALTER TABLE ADD [NewId] INTEGER ) then run the following to populate the new id column :

WITH Cte
AS
(
    SELECT *
    , ROW_NUMBER() OVER(ORDER BY [Your GUID Column Here] DESC) AS RowNumber
    FROM YourTable
)
UPDATE Cte
SET [NewId]= RowNumber
GO

There you have a new ID column that you can use a clustered primary key