How to do work confirmation by SAAS for existing PR and PO created through PAAS

Summary:

Customer implemented work confirmation process in SAAS going forward.

Content (required):

How to handled the existing PO's which already interfaced through PAAS.

Please confirm the feasbility and approach on existing purchase order .

Note: existing purchase order document style is not enabled for work confirmation.

Version (include the version you are using, if applicable): 11.13.22.10.0

Code Snippet (add any code snippets that support your topic, if applicable):

attached existing document style.