After the death of the golem, iron does not fall out. I searched the Internet, which may be why I found information that in the Quark mod in the settings you can enable the drop of iron from the golem, but it is not written how to do this. My question is: how to do it?

by default quark doesn't change this, if you're playing a modpack it could've disabled the iron drop from golems, if that's the case, you need to edit the quark config (quark-common.toml in your pack config folder), first see if Game Nerfsis set to true, if so you can disable the iron farm nerf alone by setting Disable Iron Farms to false, or you can just set Game Nerfs to false to disable them all, if it's not set to true, then there's another mod doing it.

you'll need to restart the game to have this changes applied.