Is there anyway I can compute the totalPrice of specific product?

How can I compute the totalPrice of specific item, I’m trying to multiply the quantity and the price of specific product and then POST it, but I’m having a hard time on how can I compute the totalPrice of specific item

OrderSchema.js

const OrderSchema = new mongoose.Schema({
    userId: {type: mongoose.Schema.Types.ObjectId, ref: 'User'},
    products: [
        {
            productId:{
                type: mongoose.Schema.Types.ObjectId, ref: 'Product'
            },
            quantity: {
                type: Number,
                default: 1,
            },
            sellerId: {
                type: mongoose.Schema.Types.ObjectId, ref: 'User'            
            },
            totalPrice: {
                type: Number,
                default: 0,
            }

        }
    ],

}, {timestamps: true}
)

export default mongoose.model('Order', OrderSchema)

Order.js

const handleSubmit = async (e) =>{
    
    e.preventDefault()
    if(orderSummary?.location === ""){
       toast.error("Please input location..")
    }else{
        try {
            await userRequest.post(`/order`,{
                   userId: currentUser._id,
                   products: cart.products.map((item) =>({
                       productId: item._id,
                       quantity: item.quantity,
                       sellerId: item.seller_id._id,
                       totalPrice: Number(item.quantity * item._id.price)
                       
                   })),
               }) 

           } catch (error) {
               toast.error("Please put a Location and Time!")
           }
    }
    
}

in this image, I want to get the total amount of specific product, so the first product should have a 369 .

But when I call my get all orders, this is what I get

 {
        "_id": "63b1b4de5a95bd4df7f9443b",
        "userId": {
            "_id": "63b18af8363f51fa50801dd0",
            "studentId": "1234567892"
        },
        "products": [
            {
                "productId": {
                    "_id": "63b16fc58fe585c7b81c748d",
                    "title": "asd",
                    "price": "123"
                },
                "quantity": 3,
                "sellerId": {
                    "_id": "63b160689f50f852e056afaf",
                    "studentId": "1234567890"
                },
                "_id": "63b1b4de5a95bd4df7f9443c"
            },
            {
                "productId": {
                    "_id": "63b16ff08fe585c7b81c7496",
                    "title": "asd21",
                    "price": "213"
                },
                "quantity": 3,
                "sellerId": {
                    "_id": "63b160689f50f852e056afaf",
                    "studentId": "1234567890"
                },
                "_id": "63b1b4de5a95bd4df7f9443d"
            }
        ],

    }

What I’m trying to get here when I call order.js is the totalPrice, like this example.

{
        "_id": "63b1b4de5a95bd4df7f9443b",
        "userId": {
            "_id": "63b18af8363f51fa50801dd0",
            "studentId": "1234567892"
        },
        "products": [
            {
                "productId": {
                    "_id": "63b16fc58fe585c7b81c748d",
                    "title": "asd",
                    "price": "123"
                },
                "quantity": 3,
                "sellerId": {
                    "_id": "63b160689f50f852e056afaf",
                    "studentId": "1234567890"
                },
                "totalPrice": "369"
            },
            {
                "productId": {
                    "_id": "63b16ff08fe585c7b81c7496",
                    "title": "asd21",
                    "price": "213"
                },
                "quantity": 3,
                "sellerId": {
                    "_id": "63b160689f50f852e056afaf",
                    "studentId": "1234567890"
                },
                "totalPrice": "639"
            }
        ],

    }

How are you getting the data currently ?