We have recently replaced a hub3 with a hub6 after the old one gave up.
Trying to find out how to move the 5 external addresses that were attached to the old router to the new one?
Did you get a Business Hub 6 (called the Business Smart Hub) rather than a Home Hub 6? Static IP address configuration is only possible on Business Hubs. To configure static IPs you use the hub manager, here's the on-line user guide for the BT Business Smart Hub:
How do I assign multiple Static IP addresses on the Smart Hub? | BT Business
HTH