AP invoice approval rule with PO number

Summary:

How to route approval based on Purchase Order Matching by using PO prefix number on AP invoice approval rule

Content (please ensure you mask any confidential information):

We would like to have AP invoice approval flow when it matched with PO requirement,
For example
Different type of PO may have different prefix of PO number
0606XXX
5001XXX

Could you advise whether there is any condition for purchase order number or PO prefix related on AP invoice approval rule.

Or any other advise that we can using matched PO prefix number i.e. substr(po_number,4) = '0606' on AP invoice approval rule