Origin in space

Good Morning I have encounter my first origin in space based off datum target on the part. My plan and correct me if I am incorrect is to take the points for A (3), B(2) and C(1) and use the to construct a Plane line and origin. But if I am using point on the part how then do I move that origin to it's proper place. I am not sure if I need more input from engineering or I am just not seeing it. Below it the table on the print.