@nasheayahu It's not really designed to upgrade pfSense via USB. You can kind of do it though, for instance, to convert to ZFS.
This process allows pulling the config file during installation:
https://docs.netgate.com/pfsense/en/latest/backup/restore-during-install.html#recover-config-xml-from-existing-installation
I would definitely make sure you have your own backup though. Always a good idea.
Since you have a 2100 you want the Plus software so you can open a free ticket. CE is the free, AMD64 software.