What is the format to enter in AP_INT_CDRM_PO_FORMATS Profile Value if PO# are alphanumerical ?

What is the format to enter in AP_INT_CDRM_PO_FORMATS Profile Value needed for recognizing PO# during IDR invoice import given PO# are PUR16950000001, PUR02784000001 and PURBPH000001 where -

PUR16950, PUR02784 and PURBPH are prefix (remain same whenever new PO is created) and 000001 is the incremental number (increase in incremental order like 000001, 000002 whenever new PO is created) for the PO?

Thanks.