Which file or files should I look？

[blackteapie]

If I want to make a new pillar lamp that not use battery as fuel.

I have checked ISWorldObjectContextMenu

and ISLightSource. But I didn't find anything mentioned about using battery specifically for fueling the pillar lamp. They only said about fuel the light source.

[Koregan]

Check ProjectZomboid\media\lua\client\BuildingObjects\ISUI\ISBuildMenu.lua:

 

Line 362: ISBuildMenu.onPillarLamp = function(worldobjects, square, sprite, player)

...

Line 435: ISBuildMenu.onWoodenPillar = function(worldobjects, player)

...
etc.