Merge Statement

Depends.   What are you trying to accomplish, what is the schema for all these tables, and when you execute it do you receive any kind of error message?  Mind readers we ain't.

try this

MERGE Orders AS O
USING (SELECT order_id FROM NewOrders) AS no
ON (o.order_id = no.order_id)
WHEN MATCHED THEN
    UPDATE SET o.ShippingDate = no.ShippingDate,
                 o.PaymentDate = no.PaymentDate,
                     o.PaymentAmount = no.PaymentAmount
WHEN NOT MATCHED BY TARGET THEN
    INSERT (order_id, CustomerName, ShippingDate,PaymentDate,PaymentAmount)
    VALUES (no.order_id, no.CustomerName, no.ShippingDate,no.PaymentDate,no.PaymentAmount)