How to push an object coming from postman as a number(validationError)?

My main problem is I cannot push quantity to its respective object. I am posting data in JSON format in postman like this:

  "productId":"621256596fc0c0ef66bc99ca",
  "quantity":10

my schema is:

userOrders:[
            {
                productId:{
                    type: String,
                    required: [true, "ProductId is required"]
                },

                quantity:{
                    type: Number,
                    required: [true, "Quantity is required"]
                }
            }
        ]

my controller is:

module.exports.createOrder =  async (data) => {

    let id = data.userId;
    let product = data.productId;
    let oQuantity = data.quantity;
    return  User.findById(id).then(user =>{

            
            user.userOrders.push({productId:product})
            user.userOrders.push({quantity:oQuantity})  
            return user.save().then((savedOrder, err) => {
              if (savedOrder) {
                  return savedOrder;
            } else {
                 return 'Failed to create order. Please try again';
            }
         }) 
      });

I receive an error like this:

this.$__.validationError = new ValidationError(this);
                               ^

ValidationError: User validation failed: userOrders.0.quantity: Quantity is required

I’ve tried so many things but I still cannot solve it. Any tips?