Include script files for admin submenu page

You must have created submenu page using add_submenu_page() hook, so you can use wp_enqueue_script inside callback function of add_submenu_page hook. It will load script only on your submenu page.

add_submenu_page( $parent_slug, $page_title, $menu_title, $capability, $menu_slug,'callback');

function callback()
{
//enqueue script
}

Or if you want to enqueue script in dashboard(all pages) then you can enqueue script in admin_init hook

add_action( 'admin_init', 'function_name' );
function function_name()
{
//enqueue script
}