Linked pages not working with wordpress

I used this code to create a menu page which loads mypluginpage.php and it works fine with my plugins.

I can access it from something like http://mysite/wp-admin/admin.php?page=myplugin

<?php // Add menu function myplugin_menu() { add_menu_page("myplugin", "my plugin","manage_options", "myplugin", "mypluginpage",plugins_url('/myplugin/img/icon.png')); } add_action("admin_menu", "myplugin_menu"); function mypluginpage(){ include "mypluginpage.php"; } 

Here is my issue: Inside mypluginpage.php below, I have a link that should take me to welcome.php within admin page

<?php wp_head(); ?> <a href="<?php echo admin_url('welcome.php'); ?>">Take me to welcome page within admin</a> <?php wp_footer(); 

I thought am supposed to have something like this link below which will still keep me within admin page

http://mysite/wp-admin/admin.php?page=welcome

but I got

http://mysite/wp-admin/welcome.php

which leads me to page not found

I need to have welcome.php page to called within admin. any help will be appreciated..