The importers are old, like really old; you'll need to import to something like UBB.threads v7.2 then proceed to upgrade that to the latest version (installing new styles included with the v7.7.x download when you get to that step).
You are entirely correct that the mysql file has been replaced with a mysqli one, this was part of the v7.6.0 transition (but in any case, importers should be run on v7.2).
