I don't know ho to find data which is related 3 models away

Hello i am a newbie learning back-end. I currently am doing final project for junior back-end web developer. i am doing an e-learning app. i made the following models

Admin/Teacher models

const mongoose = require('mongoose')

const adminSchema = mongoose.Schema({
    nama: {
        type: String,
        required: true,
        max: 255
    },
    email: {
        type: String,
        required: true,
        max: 100
    },
    password: {
        type: String,
        required: true,
        min: 6,
        max: 1024
    },
    createdAt: {
        type: Date,
        default: Date.now
    }
})

module.exports = mongoose.model('Admin', adminSchema)

Class models

const { type } = require('@hapi/joi/lib/extend')
const mongoose = require('mongoose')

const kelasSchema = mongoose.Schema({
    
    nama: {
        type: String,
        required: true
    },
    ket: {
        type: String,
        required : true
    },
    admin: {
        type: mongoose.ObjectId,
        ref: "Admin"
    },
    tglTerdaftar: {
        type: Date,
        default: Date.now
    }
})

module.exports = mongoose.model('Kelas', kelasSchema)

KelasTaken models

const mongoose = require('mongoose')

const kelasTakenSchema = mongoose.Schema({
    user: {
        type: mongoose.ObjectId,
        ref: "User"
    },
    kelas: {
        type: mongoose.ObjectId,
        ref: "Kelas"
    }
})

module.exports = mongoose.model('KelasTaken', kelasTakenSchema)

Nilai (Score) Models

const { string } = require('joi')
const mongoose = require('mongoose')

const nilaiSchema = mongoose.Schema({
    skor: {
        type: String,
        required: true,
        max: 4
    },
    user: {
        type: mongoose.ObjectId,
        ref: "User"
    },
    quiz: {
        type: mongoose.ObjectId,
        ref: "Quiz"
    },
    createdAt: {
        type: Date,
        default: Date.now
    }
})

module.exports = mongoose.model('Nilai', nilaiSchema)

Quiz models

const { array } = require('joi')
const mongoose = require('mongoose')

const quizSchema = mongoose.Schema({
    kelas: {
        type: mongoose.ObjectId,
        ref: "Kelas"
    },
    nama: {
        type: String,
        required: true
    },
    bacaan: {
        type: String,
        required: true
    },
    soal: {
        question:{
            type:String,
            required:true
        },
        answer:[
            {
                type:String,
                required:true
            },
            {
                type:String,
                required:true
            },
            {
                type:String,
                required:true
            },
            {
                type:String,
                required:true
            }
        ],
        correctAnswer:{
            type:Number,
            required:true
        }
    }
    // option untuk jawaban yang benar dari setiap pertanyaan
    // option: {
    //     type: Array,
    //     default:[]
    // }
})

module.exports = mongoose.model('Quiz', quizSchema)

User/Student models

const mongoose = require('mongoose')

const userSchema = mongoose.Schema({
    nama: {
        type: String,
        required: true,
        max: 255
    },
    email: {
        type: String,
        required: true,
        max: 100
    },
    password: {
        type: String,
        required: true,
        min: 6,
        max: 1024
    }
})

module.exports = mongoose.model('User', userSchema)

i am trying to make Admin/Teacher to be able to find all the score of the students he has on his class. I tried nested populate etc, but simply got lost trying to find the right method to connect admin and the scores. I dont think i can redesign the models structure as the web app is already launched and i am simply one of the back-end team members. So i hope i can find the solution in the routes