It looks like your sensor specs are:
SPECIFICATIONS
* Thread size: Male 1 1/2”
* Size:L 92x OD46 X1.5"
* Colour: Black colour
* Flow rate: 5~200L/min
* Flow Pulse: F(Hz)=(0.45xQ) +/-3% Q=L/min
* 1L water= 27Pulse
* Max. Working Current: 15mA (DC5 V)
* Min. Working Voltage: DC 4.5V
* Working Voltage: DC 5V~24V
* Load Capacity: =10 mA (DC 5 V)
* Operating Working Temperature :
* -25 Degree centigrade to +80 Degree centigrade
* Liquid Temperature: 85
* Accuracy: 3~5%
* Working environment: water, liquid, light oil etc
So for every litre of water which passes through it 27 pulses should be read.
You may need to configure at least two counters to get the result you want.
The first counter will count to 27 and then deliver one pulse to the second counter (litres cumulative counter) and at the same time reset itself to zero and commence counting again.
If you want litres per hour you may need another counter and a timer to continue counting the litres but reset itself to zero each hour.
You can keep repeating for 24hr or 7 days etc.
That’s how I do it in PLC’s so not sure how you do that using ESPhome?