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In a typical setup, the OS is on a different medium than your data so a reinstall should not wipe your data and you should be able to import the drives again after a reinstall. It is highly recommended though to make a backup in case the importing fails and you are forced to reformat.
Whilst there are surely ways to rebuild the NC databases and all to match everything exactly as before the reinstall but honestly, this is above my knowledge. I have reinstalled NC a couple of times in the past and i did always secure my data before doing so. For me, the easiest way was the connect to TrueNAS through FTP and just download the entire data-folder from NC. I then upload it into the new NC installation through the GUI after recreating the user profiles. Not very scientific but works like a charm.