how to access plugin page from link in admin menu.php of wordpress

i have written admin_url('admin.php?page=camp_create') in menu.php of wordpress to create a link which will redirect to plugin page. after clicking it it is giving an error

You do not have sufficient permissions to access this page.

link

 $menu[71] = array( __('Campaign'), 'read', admin_url('admin.php?page=camp_create'), '', 'menu-top menu-icon-users', 'menu-users', 'dashicons-admin-users' );

i want to access plugin page but an error occurs

You do not have sufficient permissions to access this page.

via Chebli Mohamed