Upgrading NAS system

I have an ex2100 & am thinking of getting an ex4100 & moving the disks over.
Will i have to reformat them or can i retain the information and just move across?
They are in jbod at present.
Have 2 other nas disks to add to system. Hoping can just slot and setup without data transferring.

had issues with roaming previously. wondered if because jbod?

As My Cloud EX2100 and My Cloud EX4100 work on different firmware so when you place drives from EX2100 enclosure, it would ask to initialize the drives and format the drives which delete all of the data stored in EX2100 recently.
Also using 2 more drives with EX2100’s two drives in EX4100 enclosure, would ask to initialize the drives to configure RAID setup in My Cloud which reformat all the drives connected in enclosure.