The third act of the Zombies mode in Call of Duty: Modern Warfare 3 is called Confrontation, and was the finale of the mode when the game initially released. This guide contains the full list of all missions in Act 3.
All Act 3 Missions in MW3 Zombies
There are 12 missions across five tiers in Act 3. Each tier of missions must be completed to move to the next one, but players can choose the order of missions to complete within each tier.