How to deal with IPv6 in Wireshark?
What you are seeing is IPv6 dns servers that your Mac is getting from your router. Note that IPv6 dns can still return IPv4 addresses so you will need to handle both sets of addresses since some servers and networks are now IPv6 only.
IPv6 is a replacement for the older and more common IPv4 that you are used to seeing. Why? Because the world is literally running out of IPv4 IP addresses and the new IPv6 is an enormously larger address space (3.4×10^38 addresses).
There is nothing wrong with your Mac. You should leave it alone. Changing that to an IPv4 address, while possible, does nothing for you. And, in fact, it would be like someone deciding to go back to horse and buggy transportation instead of his car because he thinks horses are prettier. Certainly your call and certainly possible but not necessarily the most efficient use of your time and effort.
The conversion from IPv4 to IPv6 is taking longer than many people expected but it is happening and eventually the old IPv4 addresses will not be used. My advice to you, &quot;get used to the new standard.&quot;
For some time, you might try disabling IPv6 entirely or force your Mac to use openly IPv4 based DNS services, but you will break things and be limited even today on what you can do by excluding the possibility of interacting with IPv6 networks.