Depends on where the alarm indicator light is most visible.
This is not a button, but the flashing red light to warm would-be-thieves that the car is fitted with an alarm system.
You probably will find a black box with a tangle of thin wires underneath the dash somewhere.
Would also include the remote receiver wire, motion sensor, horn assembly in the engine bay, wires for the ignition key, flasher, door ajar switch and possibly wires to a relay for flashing your driving lights.
Walter