Assuming this is a belt driven pump, look around the serpentine belt to find the pump. The reservoir is usually attachd to it with a fill cap on top.
Those came with electric or hydraulic power steering assist so it may not have one. https://my.gm.com/content/dam/gmownercenter/gmna/dynamic/manuals/2008/pontiac/g6/20 08_pontiac_g6_owners.pdf
Depends if you have a 4 cylinder or 6 cylinder.if its a 4 like mine you are like me and have the EPS power steering and there isn't a resivoir or power steering pump under hood.all electrical power steering.blows my mind because never had a car with EPS.
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