AC Voltage to Spark Plug
The usual way that a spark plug is fired is to provide a low-voltage DC pulse to an ignition coil. An ignition coil is a pulse transformer that is specifically designed for that purpose. If you search "ignition coil spark circuit" or anything like that, you should be able to find lots of detailed information with diagrams. Very little power is required. Any simple AC to DC power supply will profide a good starting point if you must use AC. Here is the basic diagram: