Hi Ludwig Reinhard ,
thanks for your response.
I disable the change management in the test environment.
in the test environment, the workflow option was hidden, and the newly created POs workflow status was Approved, and still, I was unable to delete the Pos after confirmation.
but in another environment which changes management is active, the workflow option was not hidden and the newly created POs workflow status was draft.
as I mentioned before I was able to delete the confirmed POs, I just use the "request change" option to draft the PO after that the delete option was enabled and I was able to delete it.
I think the change management was enabled when I was able to delete the confirmed POs because the workflow was enabled and the newly created POs approval status was draft