So you're trying to restore from your backup? What backup utility are you using, the downloadable contrib? Something on your host's control panel? phpMyAdmin?
Whatever the answer, your question would be better posed to someone who's responsible for that utility. The error you have sounds like the backup set the configuration_group_id for reinserting configuration entries to NULL. I believe that's okay in the latest versions of MySQL (v5.x), but not earlier versions like v3.23. This is why I always recommend phpMyAdmin for all DB editing, it's smart enough to change syntax based on your server version.
Admin > Configuration > My Store > Display Prices with Tax in Admin
Not too obvious a hint I hope...
Read the README file.
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