How to write YII module route

I have add the following code in custom-config.php of yii

'modules' => array(
        'admin' => array(
            'modules' => array(
                'slider',
                'siteSettings' =>[
                    'defaultController' => 'default',
                ],
                'menu' =>[
                    'defaultController' => 'index',
                ],
                'page' =>[
                    'defaultController' => 'index',
                ],
                'partner' =>[
                    'defaultController' => 'index',
                ],
                'blog' =>[
                    'defaultController' => 'index',
                ],
                'feature' =>[
                    'defaultController' => 'index',
                ],
                'user' =>[
                    'defaultController' => 'index',
                ],
                'testimonial' =>[
                    'defaultController' => 'index',
                ],
                'subscription' =>[
                    'defaultController' => 'index',
                ]
            ),
            'defaultController' => 'dashboard',
        ),
        ),

But when I am trying to access site.com/admin it shows This page isn’t working. My php version is 7.4 and it is running in apache.

Please suggest me a solution.