Extract the files to your CODEX save folder (typically C:\Users\Public\Documents\uPlay\CODEX\Saves\AssassinsCreedOrigins ). Backup your existing saves first!
While specific level-based save files change frequently on community sites, you can often find them at: --- Assassin 39-s Creed Origins Save Game Level 30 Codex
Unlike generic "100% complete" saves, the Level 30 Codex is valued because it leaves 40% of the game untouched. You are powerful, but you still have a reason to explore Alexandria, Giza, and the Isu tombs. Extract the files to your CODEX save folder