Step 1
Go to your child theme function.php
Path – wp-content/themes/yourchildtheme/function.php

Step2
Add these 2 lines on your function.php file

remove_action( ‘woocommerce_before_checkout_form’, ‘woocommerce_checkout_coupon_form’, 10 );
add_action( ‘woocommerce_checkout_order_review’, ‘woocommerce_checkout_coupon_form’, 5 );