understanding IP and NAT firewall

This article says:

Not sure if your wifi router has a NAT firewall enabled? Try connecting two devices to the same wifi network, such as a laptop and smartphone.

Now, on each of them, run a Google search for “what’s my IP?”

If you see the same IP address for both devices, you’re probably behind a NAT firewall.

I ran the search, and the addresses were each 38 characters long (including colons). The first 19 characters (including colons) were the same, but the last ones were different.

I've only dealt with ip addresses in format ##.#.#.###. What do my googl results mean?

It means you are using IPv6. You can try this:
check for firewall/NAT on network - Server Fault.