For this we shall be using Putty and Windows Powershell (Terminal in Linux/MacOS).
So open up Putty and SSH into your RPI using the following command:
Now to copy the keystore folder to your home directory.
$ sudo cp -r /var/lib/mysterium-node/keystore /home/pi
Make sure that it is properly copied.
sudo ls -la /home/pi
Change the ownership of the folder and files.
$ sudo chown -R pi keystore
Now you will have a keystore folder on your home directory and you are finished with
Open up Windows Powershell.
> scp -r pi@rpi-ip-address:/home/pi/keystore .
Now in your Windows user folder you will find the keystore folder with a UTC* file, you have now backed up your Mysterium node ID.