Hotwater Tank ?

I got it to come on after replacing the thermal cutoff switch know I need to work on flame it looks like a big match and not a blue with a little yellow flame. I am going to remove it and try cleaning it.
Update everything is working great thank you for all the help

If electric and gas are both on, you'll just have faster recovery and/or longer running time for hot water. Won't hurt anything. But remember to TURN OFF both before draining the water heater. Electric element can burn out in 30 seconds of less WITHOUT water on it. Running off gas(propane) allows for more amperage use in your rig.

The light doesn't come on(it's on the wall above sink right by the water pump switch.I think I may of found the problem I found what looks like a fusible link that looks burnt I think it goes to the Thermal cutoff switch so I am taking it down to are small trailer store to see if they have it or know what it is.
I found another switch under the cabinet right on the back of the unit that says on/off I think that is for electric will it hurt if I just leave it ON even if I am running on gas? its not real easy to get to do I am assuming it will just stay on
On the Thermal cutoff switch I checked it for Continuityand there was none THANK YOU everyone for your opinion and help

Mine has a switch inside in the electrical control box marked Wtr Htr.and a switch you access from the outside in the water heater access panel.Those are both for electric operation.Inside we have a red light switch like beemerphile1 above.

Is it a red switch that lights when you first turn it on? If so that is the gas. When the light goes out it indicates the flame is lit.

There is usually a separate switch for it to run on gas. Mine is on a control panel by the fridge. If you're running it on gas, there is no need to have the electric on, so that one will be OFF.