Where can i find iron in minecraft?

I need coal and iron and gold and diamond but I don't know where to find it… How can I calculate it?

Ok basically just dig down for like 15 blocks then make dig every other row hopefully you will find some iron and coal for diamond and gold I recommend finding a cave and searching on ceiling walls etc just look around deep caves hope that helped

Dig downwards.

Dig down (Not straight down or you will fall in lava), then you should hit a black/gray block once you dug for a while. Go Back up about 5 blocks and dig forward for however long you want to.