that's hard to tell...

Since the alarm system is a 3rd party equipment, it does not have a "professional look", instead, it should look like a tiny switch bought from Radio Shock.

Look for a tiny switch under (or near) the steering wheel. My switch is black.

I have another old car that also has alarm system, but the remote looks different. I tried to program my new spare remote to that old car... no, it did not work!
The other car's alarm cannot learn the signal sent by my new remote. So, don't buy the remote that is not designed for your alarm.