MyCloudEX2Ultra two steps backup

Hello all. I have an Ex2Ultra NAS and recently I bought a second one. Both 4TB
My target is to backup the first to the second one but since they are in 2 different Countries and the first has more than 3Tb of data, I would like to create first a copy, or a backup, on a usb external drive, travel to the second site, copy or move all the content of the external drive to the second NAS, so that the data transferred between the first NAS to the second from that moment onward, to update the backup, is minimal.
How do I perform such a task?
How do I perform the backup to the external drive?
Then, do I need first to create the same users, shares and permissions on the second NAS and then transfer the content from the usb drive or may I create an image to “clone” the NAS?
Finally, how do I setup the direct backup of the first to the second using a gateway to gateway VPN (possible?) (different subnets)
Anyone may help with non-too-technical terms or abbreviations and with a step-by-step procedure please?
Thank you so much in advance!
Best regards,

I have mycloudex2 and a single bay gen 2. Bewteen the two devices I setup rsync in about 5 minutes and added crontab to run daily. If these are new terms to you then I suggest you talk to a local Linux geek to help you as it’s not a simple task for a Linux/Unix newbie. You can easy brick and/or loose all your data if not familiar with Linux/Unix.

Thank you for your reply.
It was enough clear and simple, but this covers only the last step of my issue.
I need to copy first the content of my NAS to an external hard disk and then bring it phisically to the place where I have the second NAS to avoid transferring 3 Tb over the Internet.
Any suggestion for this?
I mean, of course I may copy the data only and then recreate shares folders users and permissions, but I would like to “clone” the NAS on an external usb drive and then “clone” this on the second NAS, to have identical content before setting-up the automatic backup


You could refer to the following link:

Thanks a lot! This is what I was looking for