Put a data type in the @user_id parameter. I assumed that it is an INT since it is an ID. And remove the extra , after the "ON O.order_id = O_P.orderID". The corrected query should look like this:
CREATE PROC sp_seeOrder
@user_id INT
AS
SELECT
O.order_id, O.order_quantity, O.user_id, O.Status, O.order_date, O_P.orderID,
O_P.product_code, P.product_id, P.product_name, P.price
FROM Orders AS O
FULL JOIN Ordered_Products AS O_P
ON O.order_id = O_P.orderID
RIGHT JOIN Products P
ON O_P.product_code = P.product_id
WHERE user_id = @user_id;
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