Query data laravel

i want to know how get this working in laravel :

I have two tables: "orders" and "delivery_boys" .

When an order is created i want to get "id" in table "delivery_boys" that correspond to the "store_id" in the "order" table.

which looks like that in mysql SELECT `id` FROM `delivery_boys` WHERE store_id = '3'

Thanks for your help.

I use this fonction:

 protected $table = 'orders';

   public function addNew($data)
   {
      $user                = AppUser::find($data['user_id']);


      if(isset($data['address']) && $data['address'] > 0)
      {
          $address = Address::find($data['address']);
      }
      else
      {
          $address = new Address;

      }

      $add                 = new Order;
      $add->user_id        = $data['user_id'];
      $add->store_id       = $this->getStore($data['cart_no']);
      $add->d_boy          = $add->?????;  <---- here i want to add from "delivery_boys" table the "id" that correspond to the "store_id" added just above from the "order" table ---->

      $add->name           = $user->name;
      $add->email          = $user->email;
      $add->phone          = $user->phone;
      $add->address        = $address->address;
      $add->lat            = $address->lat;
      $add->lng            = $address->lng;
      $add->address        = $address->address;
      $add->d_charges      = $this->getTotal($data['cart_no'])['d_charges'];
      $add->discount       = $this->getTotal($data['cart_no'])['discount'];
      $add->total          = $this->getTotal($data['cart_no'])['total'];
      $add->payment_method = $data['payment'];
      $add->payment_id     = isset($data['payment_id']) ? $data['payment_id'] : 0;
      $add->type           = isset($data['otype']) ? $data['otype'] : 1;
      $add->notes          = isset($data['notes']) ? $data['notes'] : null;
      $add->save();

via Chebli Mohamed