Upgrade Synology DS218+ single drive SHR - (no data protection) to two larger drives with data protection

I am looking for advice on upgrading a Synology DS218+ that currently has only one 10TB drive. I need to upgrade this to two 18TB drives.
I’ve researched the following scenarios and have yet to find confidence on a procedure.

  1. Add one of the 18TB disks as a second drive in the Synology but that would only add the 18TB as additional available space - making 28TB available with no data protection. If I were to enable data protection it would remove 8TB of the new 18TB drive leaving me with only the 10TB space available. Then when I add the 2nd new 18TB drive it too would only have the 10TB space available (then I would have two 18TB drives installed with only 10 TB of space - and that’s no better than where I started)

  2. Is there a way to clone or image the 10TB drive to one of the new 18TB drives. Of course, I will also need to expand the available partition size from the 10TB to the full capacity of the 18TB as well. However, my research on what tools to use for this on drive from a Synology NAS have not been successful. I’ve used common imaging tools like clonezilla, drive image xml, shadow protect, gparted, acronis, n-able backup, etc. for Windows partitions but I am new to Synology and the nuances of how to image or clone it’s drives

Am I right about my above assumptions?
Any help will be greatly appreciated.
Oh, and Mery Christmas everyone!

I know when you setup a mirror between different sized drives it will only have the amount of storage of the smallest drive in the mirror, I am not sure if it will expand when that smaller drive is replaced with a larger one.

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For those that face this challenge I’m happy to report that it will in fact expand when the smaller drive is replaced with a larger one.

I simply added the first 18TB drive to the Synology that only had one 10TB drive SHR choosing to expand storage. Then I let it do its thing. When finished as expected I had about 10TB storage (one 10TB and one 18TB drive). Then I replaced the 10TB with the 2nd 18TB and let it do its thing again. When it finished, I had my 18TB storage across both drives in the Synology. It took around 3 days per operation but no need to image the drive or do something else even if you start off with a single drive unit with SHR.