Hello @sinu 

Use the below code, it works tested.

<form class="form-inline">
  <div class="form-group">
     <input type="text" placeholder = "Enter tracking code" class="form-control"> 
    </div>
     <button type="submit" class="btn btn-primary mb-2">Submit</button>
     <p> Please enter a tracking code to track a new shipment</p>
  </form>

Mark my response as both helpful and correct based on the impact.