Hi Edward,
no worries, now I understood.
Yes you can use the preparation script to bring your system to currently DietPi v6.4: https://github.com/Fourdee/DietPi/issues/1285
But note, that this will purge most software packages and data, so no guarantee that any of your manual adjustments/settings will survive. The scripts intention is to turn no-DietPi images into DietPi, not for upgrading 
.
To save your manual settings/data, please do a full system backup (e.g. dietpi-backup) and safe it together with /mnt/dietpi_userdata/ on an external drive. From there you can recover data and settings, lost during preparation script process. Please also read: https://dietpi.com/forum/t/need-help-before-update-to-dietpi-v6-x/1928/1
Best regards