Answers for "laravel Target class [PageController] does not exist."

laravel 8 Target class [FormController] does not exist.

use App\Http\Controllers\UserController;

Route::get('/users', [UserController::class, 'index']);
// or
Route::get('/users', 'App\Http\Controllers\UserController@index');

Target class [SallyController] does not exist.

//In laravel 8 uncomment  protected $namespace='App\\Http\\Controllers';

target class admin homecontroller does not exist laravel 8

Route::get('/home', 'App\Http\Controllers\HomeController@index')->name('home');

Target class [AppController] does not exist.

public function boot()
{
    ...

    Route::prefix('api')
        ->middleware('api')
        ->namespace('App\Http\Controllers') // <---------
        ->group(base_path('routes/api.php'));

    ...
}