The battery does not have enough power to support motors. Voltage and current are very different. Many years ago Mr. Ohm stated a law about current and voltage, and that law is still valid. I highly recommend you look at it and the relationship between voltage, curent, and wattage. Your motor needs '?' watts at a maximum of 3V. Your L298N will drop about 3 Volts. Take your volt meter (you have one correct) and measure the motor voltage, I expect it to be in the low 2V range. Not throw away that 9V battery and get a decent power supply and your motors should run if connected correctly.