If you are installing , you specifically need the zone/all folder containing checksum-verified .ff files.
In the Call of Duty engine, "zone files" (usually found in the zone folder) are highly compressed archives that contain the essential data for specific parts of the game. This includes: Cod Mw3 Zone Files Download
Key points
Launch Call of Duty from your console or PC. Open the Menu and select Manage Files. Select Manage Files. Activision Support Call of Duty: Modern Warfare III Installation and Setup If you are installing , you specifically need