How to copy directly from older NAS to EX4100?

I would like to copy all my data from an older NAS (QNAP) to my new EX4100 directly.
Is it possible to do that without all data going through my laptop?
My think is that hopefully, a direct copy would be faster - I’ve got 6 TB of data.

Both NAS’s are connected to the same router (Fritzbox) via Ethernet cables.
One idea would be to mount the old NAS on the EX4100, and launch an rsync command from the command line of the EX4100.
But I don’t know how to mount the old NAS on the EX4100.

Could some kind soul please help with that?

Or is there another , similar solution?

Thanks a lot in advance.

Best regards, Gabriel