child advancement help

I'm having trouble with making a child advancement. I have the parent one working, but that it is how far I could get. 
{
    "display": {
        "icon": {
            "item": "minecraft:creeper_head"
        },
        "title": "Creeper Collector",
        "description": "AWWWW MANN",
        "frame": "task",
        "show_toast": true,
        "announce_to_chat": true,
        "hidden": false
    },
    "criteria": {
        "root": {
            "trigger": "minecraft:inventory_changed",
            "conditions": {
                "items": [
                    {
                        "item": "minecraft:creeper_head"
                    }
                ]
            }
        }
    },
    "parent": "tutorial:tutorial/root"
}   
this is how far I got with misode. for my parent I used the name of the data pack, then the folder that contains the root json