Missing required parameters for [Route: catagory.show] [URI: post-ad/{catagories}] laravel 5

I am working with laravel 5.6 and need show file in catagory.show file using CatagoryController show function,

public function show($id)
    {
         $catagories = Catagory::find($id);
        return view('catagory.show')->withCatagories($catagories);
    }

this is my route

Route::get('post-ad/{catagories}', [
    'uses' => 'CatagoryController@show',
    'as'   => 'catagory.show',

]);

and my link page to this page link is

@if(isset($catagories))
 @foreach ($catagories as $cata)
<div class="col-md-9">
  <div class="col-md-3 text-center">
    <a href=""><img src="" alt="profile Pic" height="50" width="50" class="center-block"></a>
    <div><a href="/post-ad/"></div>

  </div>
  @endforeach
   @endif

but I got following error msg,

UrlGenerationException

Missing required parameters for [Route: catagory.show] [URI: post-ad/{catagories}].

how can fix this problem?

via Chebli Mohamed