You need to find out if it's aftermarket (it probably is TBH). If so you'll need an auto electrician to remove it. They are more rouble than they are worth.
That said, I had one in an Austin Montego - a car notoriously easy to steal. I put the alarm and siren high up in the passenger footwell. When it went off you could not sit in the car. The car was broken into and moved about 30 ft. Tea leaves fled leaving the doors open.