dometic 300 refer

The other button purges the gas, hold it in while you push the striker in and out till the gauge goes in the green, I believe the instructions read not to hold the gas button in more than 30 seconds at a time.

One operates the piezo ignitor
Other one operates the gas safety valve....holds it open until flame lights off and thermocouple sends millivolt signal energizing the electro-magnet in gas safety valve which then holds valve open until temp set point is reached

Thank you , so to run on ac all I got to do is turn that switch to the picture of an electric plug ?

YES