Hi Atul,
You can use the method ORDERADM_H or any other method based on the field that you are copying.
For ex: If your field is part of the ORDERADM_H object then you can use this method or else you can use any of the other appropriate methods. Almost all the objects of CRM are part of this BADI.
In the COPY method, you can place any additional validations whether a copy should happen or not (if you have any such requirement).
Hope this helps.
Thanks and regards,
Preeti