The CPU has a CF (CompactFlash) memory card, which you can just unplug (after powering off) and transfer to the new CPU.
Automation Help: X20CP148x Operating and connection elements
You can take a disk image of the CF-card to have as a backup with the tool of your choice. B&R has a tool called Runtime Utility Center (RUC), which can do this, use the Create / Restore Disk Image command from the main menu. RUC is automatically installed when Automation Studio is installed.