Disabled buttons and fields on sales Confirmation

Hi ,
I am working as technical consultant , and I have only 6 month experience . But i have a work on Dynamics 365 FO where i have to create transfer order and disabled all button and fields of sales table form after sales order confirmation ,
So can any one please help me , should i take extension of Closeok method of SalesEditLines form or any other options is there because there exist a record in custconfirmjour form.