As per our understanding, You want to delete the PO and Inbound delivery ?
If yes, Before delete the PO and Inbound delivery , You need to reverse (Reject) the Vendor SO,DO and Invoice.
Please do the same and confirm.
Else, If you confirm this orders (Vendor SO,DO and INVOICE) are not required, Please give the permission to delete the PO and inbound delivery directly at our end.
We will do the same and confirm.