how do i find vanilla assets in the workspace

so i want to make it so if you drink milk it wont get rid of a potion effect ive made and i have a eneral idea on how to do so i just need to edit some of vanilla minecrafts milk code into not deleating the effect

i just need to get normal minecrafts milk into the works space any idea on how to do so or other ways i can make it so milk wont clear the effect?