For baremetal it was my method with APRL/DS3622 on 10 disks (20TB) working firstly with JunLoader under DS3617.   Preparation  1)    If your old SYNO Xpeno working OK, should be easy to migrate in a new DSM if you have your data in different Volumes and Groups . For reduce risks prepare volumes matching HDD, with Group/Volumes . Will be better if you have NAS Stored with 1Volume as small Group, 2Volume as middle Group and 3Volume as BigGroup 2)    Not necessary make a backup