Upgrade from PI 7.1 service pack 18 to 7.31 DUAL STACK

Hi Experts,

   My client is on SAP PI 7.0 service pack 18. We need to migrate to PI 7.31 dual stack. Just want to add that we have both A2A and B2B interfaces along with the RFIF adapters ( Design of redirect URL for RNIF scenarios (B2B) on SAP 7.0.

I request the experts to provide the approach for the migration to SAP 7.0 to SAP 7.31. It would be of great help If I get any document regarding the same.

Regards

Veeru