Confwiz?!
First you should do a snapshot and a backup, as you said. And preferably transfer them from the device. But you cannot import snapshot/backup created for R77.30 version into R80.10.
Then, it seems you need to create a temporary R77.30 management server (distributed deployment). It could be a virtual machine with a clean install. It is not clear if you have several standalone devices, each with its own local management server, or only one standalone device to which several firewalls are connected.
There is sk61681 which explains how to migrate from standalone device to separate management server on R77.30. You need also to collect cpinfo, as it is written in the SK (although, I am not sure why).
To export the security management part (Policies, Firewall and NAT rules, Objects and services) you should use R77.30 migration tools (migrate export command). Then do some manipulations with text files and import it to the temporary R77.30 machine with migrate import.
Then you use R80.10 migration tools to export database from temporary R77.30 machine and import it to the newly installed Smart-1. Don't forget to install the latest Jumbo Hotfix on it too.
There is a simpler way if you need to save only rules and objects (without certificates, users, some specific global settings). Use cp_merge export_policy to export only firewall and NAT rules (sk33751), copy $FWDIR/conf/objects_5_0.C file containing all objects and services from the old R77.30 device. Then use a temporary R77.30 installation configured as only a management server to import objects with cp_merge merge_objects and then import cp_merge import_policy. Delete an object of old standalone device and create new firewalls objects. Then use R80.10 migration tools to export database from temporary R77.30 machine and import it to the newly installed Smart-1.