File to import not found or unreadable: bootstrap3/bootstrap/mixins in rails 3.2

I get this error "Sass::SyntaxError in Users#index" when the submit button in clicked and next page is loaded.

I have used Ruby - 2.2.4 and Rails - 3.2.2 in my application. Below are my errors and related code. If someone had the same issue before and fixed it please let me know the solution. Thank you!!!

In my gemfile, this is the version of sass-rails:

gem 'sass-rails', '~> 3.2.6'

This is the error I get in the page:

    Sass::SyntaxError in Users#index

Showing /Users/Joe/Documents/foodsapp/app/views/layouts/v3.html.haml where line #39 raised:

File to import not found or unreadable: bootstrap3/bootstrap/mixins.
Load paths:
  Sass::Rails::Importer(/Users/Joe/Documents/foodsapp/app/assets/stylesheets/v3.scss)
  /Users/Joe/Documents/foodsapp/vendor/assets/stylesheets
  /Users/Joe/Documents/foodsapp/lib/assets/stylesheets
  (in /Users/Joe/Documents/foodsapp/app/assets/stylesheets/v3.scss)

In /Users/Joe/Documents/foodsapp/app/views/layouts/v3.html.haml, line #39 the code is :

39  = stylesheet_link_tag('v3')

In v3.scss I have imported the file, the code is:

@import 'v3/mixins';