The oil capacity for a Peugeot Boxer 2.2 gearbox varies slightly depending on the specific gearbox type fitted. There isn't a single answer.
You must consult your vehicle's owner's manual. This manual will specify the exact oil type and quantity required for your particular gearbox.
Trying to find the capacity online without knowing the precise gearbox code is unreliable and could lead to incorrect oil filling, potentially damaging your transmission.