Note that a VM can be connected to more than one network, and a network can be connected to more than one router. Ergo, a VM can be connected to numerous routers.

Step 1: The command openstack server show tells you the network(s) to which the instance is connected. See the field addresses.

Step 2: The command openstack router show tells you the network(s) to which a router is connected. Alternatively, you should be able to add network information to the openstack router list command, using the -c option, but I currently don't know exactly what is the correct column name.

Another option for step 2 is openstack port list. You can add device_owner and device_id to the columns. Device-owner tells you which ports are owned by a router, and device_id tells you which router that is. The networks that ports are connected to are also displayed.

Step 1 gave the list of the networks to which the instance is connected, and step 2 the list of the routers including their networks. You need to combine the two.

I would agree that it is easier to use a network diagram. A great illustration of "a picture says more than a thousand words".