JS - there is a reason for the standard protocol of identifying your model/year 911 when asking questions here.
Plus, since you have AN lines, you aren't dealing with stock fittings, so you need to identify what was modified.
How, otherwise, could anyone give you accurate information?
Factory front fender coolers have the inlet and outlet on the top of the tank, so this doesn't look at all factory. Is it located under the left front fender? Supplementing one on the right side?
However, why not just take off one of the hose fittings and measure? You can easily find silhouette pictures of the AN sizes. However, your guess of -12 is a pretty good one. You should not need any adapter - whatever that blue fitting is, it has an AN male end on it.