How can i save a data from collection into other collection

i habe the collection of drinks , and the collection of order but i am not sure about how take order.

i wanna save a order with drinks, and the form input “cantidad” is the number of drinks, so the price x cantidad = $, i need to show the total cost of an order, how can i do this?

thanks for the help

I have the following simplified document i am using Meteor js with iron

the insert_order.html

<template name="InsertOrder">



  <div>
  <table class="table table-hover">
        <thead>
          <tr>
            <th>Nombre</th>
            <th>Valor</th>
            <th>impuesto</th>
            <th>cantidad</th>

          </tr>
        </thead>
        <tbody>

          {{#each drinks}}
            <tr>
              <td>{{nombre}}</td>
              <td>$ {{price}}</td>
              <td>{{impuesto}} %</td>
              <td><form class="new-order">
<p><input name="cantidad" type="number" placeholder="Cantidad" /></p>

</form>

</td>
            </tr>
          {{/each}}

        </tbody>
      </table>

</div>
<div class="form-group">
    <button type="submit" class="btn btn-primary" data-action="drink/add">Pedido</button>
    <button type="reset" class="btn btn-default" data-action="order/reset">Reset</button>
  </div>

</template>

the js

the insert_order.js

Template.InsertOrder.events({
'submit .new-order'(event) {
    // Prevent default browser form submit
    event.preventDefault();

    // Get value from form element
    const nombre = nombre.drinks;
    const price = price.drinks;
    const impuesto = impuesto.drinks;
    const number = target.number.value;
    //const target = event.target;

    // Insert a task into the collection
    Order.insert({
      nombre, price, impuesto, number, 
      createdBy: userId
    });



    // Clear form
    //target.text.value = '';
  },

  "click [data-action='drink/add']": function () {
    if 

  }

});


/* InsertOrder: Helpers */

Template.InsertOrder.helpers({
        drinks: function(){
        return Drinks.find();
    }


});

drinks - collections


Drinks = new Mongo.Collection('drinks');

Drinks.attachSchema(new SimpleSchema({
  nombre :{
    type: String,
    label: "Nombre",
    max: 100
  },
  ingredientes:{
    type: String,
    label: "Ingredientes",
    max: 1024
  },
  price:{
    type: Number,
    label: "$Valor",
  },
  impuesto:{
    type: Number,
    label: "%impuesto",
  },

  createdBy: {
    type: String,
    autoValue: function() {
       return this.userId
    }
  }
}));

order collection

Orders = new Mongo.Collection('orders');

Orders.attachSchema(new SimpleSchema({

  costo:{
    type: Number,
    label: "$Valor",
  },
  impuesto:{
    type: Number,
    label: "%impuesto",
  },
  cantidad:{
    type: Number,
    label: "cantidad",
  },

  createdBy: {
    type: String,
    autoValue: function() {
       return this.userId
    }
  }
}));

You shouldn’t pass prices from the client down to the server for orders. You should have a price listed for each drink in the “drinks” collection, so you pass the _id of the drink and a quantity to the server, and calculate the total price on the server, and create an order based off of that.

so, please help me, how i put _id. to the server? thanks
and how can i take the order from {{#each drinks}}? how can use this.?