You need to use any of this module

  

[Nice Menus][1]

> Nice Menus enables drop-down/right/left expandable menus. It uses only
> CSS for most browsers, with minimal Javascript for IE6.

 

[Superfish Menu][1]

[Responsive Dropdown Menus][2]

> > Responsive Dropdown Menus provides a new menu tree rendering to make
> > responsive, drop-down enabled main menu possible on any theme.
> 
>     Provides new menu blocks for each menu.
>     All module blocks add dropdown menu support and responsive menu toggles.
>     Supports menu attributes

  [1]: https://www.drupal.org/project/superfish
  [2]: https://www.drupal.org/project/responsive_dropdown_menus