Current drawn by MQ9 Sensor
The MQ-9 uses a heater (a filament lamp more than likely) to produce a broad band of infra red spectrum. The quantities of gas present of the right molecule will absorb some of that light at a certain wavelength and this allows the sensor to estimate the gas mix percentage. The data sheet shows this: -


I would like to be sure about the current drawn by this sensor, the
datasheet doesn't tell anything about that

The heater voltage is 5 volts and the heater resistance is 33 Ω hence, the current is 151.5 mA typically.
RL doesn't play a role in the dominant current consumption of the device.

It says the power Ps heating consumption is about 340mW

I expect that is an average power based on something around a 50% duty cycle (see picture below) or maybe the heater resistance rises as it warms and thus the power stated (340 mW) implies a hot heater resistance of 73.5 Ω.

The picture above taken from this much better data sheet.