The crankshaft position sensor (CKP) on a 2002 Dodge Dakota 3.9L V6 is located on the
passenger side of the engine,
near the front of the engine block. It's usually positioned fairly low, near the bell housing where the transmission connects to the engine. You'll likely need to look underneath the vehicle to access it properly.
Because of variations in specific engine configurations, a picture from a repair manual or a quick online search showing the location on a 2002 Dodge Dakota 3.9L V6 engine would be helpful for precise identification.