Thank you i had a look found its label CHA_FAN on the boardWelcome to the forums, newcomer!
Turn to page 1-4 in your motherboard manual, you should be looking for the PWR_BTN mentioned on the motherboard PCB. PWR is the +ve terminal(or the end with an arrow on the case connector) and GND is the terminal without any labelling.
Are you sure you are not looking for pwM header ? It's 4pin header for fans.Thank you i had a look found its label CHA_FAN on the board