how much force is required to lift the load
It's not clear what the measurements are. It looks like they mean the handles are 6 feet from the wheel.
I'm not going to give you the answer, but you can figure out the torque (or moment-arm) by multiplying force times distance to get foot-pounds. 360 pounds placed 1 foot from the wheel makes 360 foot-pounds of torque.
You then divide to get the force needed to balance this, using the length of the handles.