How can I load script and style in specific page in the back-end?

So simple I will explain it step by step:

1. First, use the $hook variable that is WordPress default like this:

   function the_themescripts($hook) {
       echo $hook;
   }
   add_action( 'admin_enqueue_scripts', 'dr_theme_options_style_scripts' );
   

2. Now go to custom page in your admin WP Dashboard and at the top you will see something like
   toplevel_page_your_theme_page_slug if it does not visible to you try to inspect element and see after tag copy that and use like this.

3. Use of $hook variable. Use it inside the if else loop

   function the_themescripts($hook) {
     echo $hook;
   
     if ($hook == 'toplevel_page_your_page_slug') :
         // enqueue your script/styles here for your first page    
     endif;
   
     if ($hook == 'your second page slug' ) :
         // enqueue your script/styles here for your first page
     endif
   }
   add_action( 'admin_enqueue_scripts', 'the_themescripts' );
   

Hope this explanation helps:)