To find it, look for a heavy-duty cord plugged into a receptacle somewhere near the front of the engine. It might be tucked up against the radiator, near the firewall, or even slightly hidden behind other components. It's usually a fairly thick cord, and the receptacle will be a distinctive shape.
If you can't locate it easily, referring to your owner's manual is highly recommended. The manual will have a diagram showing the location of the block heater cord specifically for your vehicle. You could also search online for pictures or videos showing a 2009 Ford Escape block heater cord location.