Laravel.54 pass data to action controller

I need to get 'mp3' value in controller ! ( to check posts from mp3s type )

my post types : video, album , mp3

(web.php)

Route::group(array('prefix' => 'mp3s'), function($pt) {
    Route::get("/", "PostController@archivePosts");
    Route::get("mp3/{slug}", "PostController@singlePost");
  });


Route::group(array('prefix' => 'albums'), function($pt) {
    Route::get("/", "PostController@archivePosts");
    Route::get("album/{slug}", "PostController@singlePost");
  });


Route::group(array('prefix' => 'videos'), function($pt) {
    Route::get("/", "PostController@archivePosts");
    Route::get("video/{slug}", "PostController@singlePost");
  });

via danial dezfooli