I have never seen a 110v oven ( But i aint seen everything) There is a tag or label on the oven somewhere that will tell you the Voltage and amp draw of the oven. If you cant find it and know what make and model oven ,Google it and you can find out there.
Wire size doesn't really tell you anything.
Did a little checking ,They do make 110v ovens But they are not common. If you look at the wires to hook up the oven ,
If it's 110v the wires should be ,Black - White- green.
220v should be black - red - green or black - red - white -green.
Hope this helps