Schema Layout:
const mongoose = require("mongoose");

module.exports = function(db) {

let gameSchema = new mongoose.Schema({

opponent: String,
location: String,
date: String,
completions: Number,
attempts: Number,
yards: Number,
touchdowns: Number,
interceptions: Number,
});

let quarterbackSchema = new mongoose.Schema({
firstName: String,
lastName: String,
school: String,
age: Number,
hometown: String,
games:[gameSchema]
});

{
"_id": {
    "$oid": "5c0a551df8555c1c1ef0c101"
},
"firstName": "Pepper",
"lastName": "Princess ",
"age": 14,
"hometown": "Farmville, Ms",
"school": "Farmers School of Important Stuff",
"games": [
    {
        "_id": {
            "$oid": "5c0ca5ba7213fe6a5f52848c"
        },
        "opponent": "Crock McSnagglebite",
        "location": "Pattys Putrid Flower Garden",
        "date": "1/23/2020",
        "completions": 777,
        "attempts": 777,
        "yards": 777,
        "touchdowns": 777,
        "interceptions": 777
    }
],
"__v": 1
}

Quarterback.find({_id: req.body.id}).then(function(Results){});

 Quarterback.findOne({_id: req.body.id}).then(ect...

 Quarterback.findById({_id: req.body.id}).then(ect...