Getting WiFI to outbuilding using ethernet

I have an internet provider in my main house (Century Link). This provider installed a new router and modem. I have a new auxiliary dwelling on my property and the electrician installed an ethernet connection from my existing modem to the outbuilding. Using information from the internet I connected the existing modem to the ethernet plug that runs to the new building. I have installed my old router (previous internet provider) in the out building. I can use the out-buildings router address (192.168.1.1) and see and connect to the router on my computer (including logging in with an administrator account). My problem is that I do not get an internet connect through this router.

I am trying to determine why I do not get an internet connection with this setup. I do not know whether my old router is incompatible with the new modem/internet provider or if I just have a wiring issue. Any help is appreciated. Here is the modem. Here is the Century Link router Here is my old router that I want to use in the outbuilding (Netgear 80)

If you do want to set up the Router to Router connection, use method 1 in this link Router to Router Setup

Note that the connecting cables must be in the proper ports, and the old router must be configured to extend the network.

Welcome to networking.

What you need in the outbuilding is a hub, or an improved hub called a switch, and a switch can include a WiFi Gateway (which simply adds the WiFi transport layer to the existing network).

The problem is, you are using none of those things, you are using a router which is designed to establish local networks, not extend them.

Now, the old router certainly contains all the necessary hardware bits to do what you want. However, it will need to be configured to do that, and by your stated skill level I'm guessing you're not there yet. For that matter the software provided in the router may not stretch that far.

But that's what I would do. Re-configure the router so it acts as a switch and a WiFi bridge, i.e. it is an invisible part of the same subnet (192.168.0.0/24 probably), it doesn't mess with the IP level of the stack, and simply forwards packets to the new router. The new router is the one assigning IP addresses in the subnet.

This will also give better latency and less complications... since you won't be doing NAT on top of NAT.