Salut Sergiu,
E chiar simplu.
Take nanoboot (last version), write it on another USB stick, and boot it.
After boot, use the latest .pat file (4482) and try to upgrade your DSM with Synology Assistant or the WebGUI. The system will mention if your data is migrant able or not. You can continue (there is ALWAYS a risk) or you can cancel the upgrade.
And by the way, there is always a risk with standard Syno boxes and original DSM, but definitively the risk is is smaller.
Succes!
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