How to find the IP of a Minecraft server

How do I find the IPv4 address of a Minecraft server (e.g us.mineplex.com, mc.hypixel.net)?

I need to do this because I am testing something for my own server.

Simple! Just open up a command line/terminal window (doesn't matter what operating system) and type:

ping <your server address here>

That should work!

Another alternative is to use nslookup which queries the name directly from DNS:

C:\> nslookup google.com
Server:  UnKnown
Address:  2601:647:4a03:6e2b:9610:3eff:fe0e:6c13

Non-authoritative answer:
Name:    google.com
Addresses:  2607:f8b0:4005:801::200e
          216.58.194.174

This shows the IPV6 address followed by the IPV4.