Not getting any information

I hope this plugin is still being supported. I’ve been trying to extract data using this but it’s not echo’ing any info back. I know I’m doing something wrong.

I add <?php if ( function_exists('get_thumbnail_field') ) get_thumbnail_field(); ?> but nothing shows up.

When I add <?php if ( function_exists('the_thumbnail_field') ) the_thumbnail_field(); ?> I get an error – which is this:

Fatal error: Uncaught Error: Call to undefined function get_post_thumbnail_field() in C:\xampp\htdocs\wordpress\wp-content\plugins\thumbnail-field\thumbnail-field.php:64 Stack trace: #0 C:\xampp\htdocs\wordpress\wp-content\themes\harshclimate\single.php(13): the_thumbnail_field('description', 45) #1 C:\xampp\htdocs\wordpress\wp-includes\template-loader.php(74): include('C:\\xampp\\htdocs...') #2 C:\xampp\htdocs\wordpress\wp-blog-header.php(19): require_once('C:\\xampp\\htdocs...') #3 C:\xampp\htdocs\wordpress\index.php(17): require('C:\\xampp\\htdocs...') #4 {main} thrown in C:\xampp\htdocs\wordpress\wp-content\plugins\thumbnail-field\thumbnail-field.php on line 64