How I want to sort my custom column contain string date with format j F Y

my column data contains string example "21 januari 2021", how I can change the format to date so I sort it.

My value from postmeta with meta_key "datepicker".

here my code:

    add_action( 'pre_get_posts', 'manage_wp_posts_be_qe_pre_get_posts', 1 );
function manage_wp_posts_be_qe_pre_get_posts( $query ) {


   if ( $query->is_main_query() && ( $orderby = $query->get( 'orderby' ) ) ) {

      switch( $orderby ) {

     
         case 'delivery_date':

            // set our query's meta_key, which is used for custom fields
            $query->set( 'meta_key', 'datepicker' );

            $query->set( 'orderby', 'meta_value' );
            break;

      }

   }

}

how I can orderby meta_valuewith format date?