How to replace existing HDD storage (RAID 1) with a bigger one

Hi all,

I need your help , i have one freenas system with 2 x 500 GB of HDD , we build this freenas for nextcloud apps on the jail.
i set 2 x 500 GB of HDD as mirror ( RAID 1 ) .

Now , i need to replace both of hdd with the 2 x 6TB of HDD.
Please let me know , how can i replace 2 x 500 GB of hdd with 2 x 6 TB of hdd , without reinstall freenas or nextcloud on jail, because the nextcloud already running, and users already upload their file to nextcloud.

here the screenshot of my...

How to replace existing HDD storage (RAID 1) with a bigger one