I tried drag and dropping the realm on to the drive but it doesn't work, I only want to save my realm to a USB so I can make another without losing it.
That means Realms are stored online, meaning the world is not on your PC, but rather on Mojang's servers, so that they can be accessed by any of the Realm members.
They can be accessed by other realm members, but unless they've been given manager privileges, all they can do is join the realm server. Without access to the management interface, they can't download the world^.
^There's other ways, but we won't get into that.
I tried drag and dropping the realm on to the drive but it doesn't work.
Of course it wouldn't work. You can't drag a server instance onto a USB drive; that'd be absurd.
How do I download my world and save it to a USB drive?
- Go to your Realms Management Interface. (The wrench symbol)
- Go to your "World Backups".
- Click on "Download Latest".
Follow the instructions on screen, and Minecraft will save a copy to your Single Player worlds.
From there, you can copy it out of your Single Player worlds folder and into wherever you want.
On Windows, it is located at:
On Mac, it is located at:
~/Library/Application Support/minecraft/saves, and
On Linux it is located at:
~/ is your home directory)
You'll find that the downloaded world retains all Multiplayer data (sans ownership permissions), so you can simply plug this world into a dedicated server and it'll remember all your friends' progresses.
Images stolen from here