Netgear Orbi Wifi 6 RBK853 Multiroom - How many cables needed?

Hi community!

I have a Netgear Orbi Wifi 6 RBK853 Multiroom 3 pack. I'm confused how many UTP cables I need going to the Router (on the UTP1 route in the drawing). One cable for WAN and one UTP cable for LAN? Or is 1 UTP cable enough? 

The situation:

I have 3 UTP cables starting in 1 location where the ISP WAN comes in. This is not the location of the Orbi router.

I have a Netgear nighthawk R7000 lying around that can connect all together?

There is 1 router and 2 sattelites in different locations than the ISP router.

The question:

Do I need 2 UTP cables to the Orbi Router (one for the WAN port and one for the ethernet backhaul as described here) or can  1 utp cable do the job?

I would like to avoid having to install a 2nd cable to the orbi router.

Is that possible?

Thank you!