You get the data to the new My Cloud EX2 the same way you got the data to the older My Cloud devices, COPY and PASTE or DRAG and DROP between the two devices. You will want to do this from a computer that is connected via Ethernet wire cable to the same gigabit capable router (or gigabit network switch) the My Cloud devices are connected too. You can even Map the Shares to make things somewhat easier. If you have a lot of data it will take a very long time to copy that data from one My Cloud to another.
One can use software programs like TeraCopy (https://www.codesector.com/teracopy) or Free File Sync (https://freefilesync.org/) to help copy from one My Cloud to another from your computer.
There are a number of other methods to copy data from one My Cloud to another such as the method the previous poster mentioned using a USB hard drive attached to the USB port of the My Cloud device. And there are methods that involve more technical knowledge. This other methods includes configuring the EX2 Ultra such that it can be used as a designation target for Safepoint/Backup from the older OS3 My Cloud devices. One may have to enable SMB1.0 and or NFS on the EX2 Ultra Dashboard > Settings section for the older My Cloud units to see and access the Shares on new EX2 Ultra. Also one may have to set the EX2 Ultra Shares to Public not Private (password protected). Other methods include using SSH to trigger an Rsync between the two devices but that requires additional computer knowledge and skills.
How to map a My Cloud or NAS device on Windows
https://support-en.wd.com/app/answers/detail/a_id/9323
How To Map a My Cloud or NAS Device on macOS
https://support-en.wd.com/app/answers/detail/a_id/24148
