There is no way to measure how many hertz make a watt. While both may represent measurements of electricity, or similar phenomena, they are not able to convert to each other.
Hertz are the international system of units measurement of the number of cycles per second or frequency. This is most commonly used to represent alternating electrical currents, sound or electromagnetic waves. Watts are the international system of units measurement of electrical power. Watts measure real power, while volts and amps measure apparent power. Watts are commonly used in association with electrical heat generation, consumption and power ratings for electrical devices.