cart.php

//Add to functions.php

<?php 
function add_number_of_cart_items() {
  global $woocommerce;
	$cart_count = $woocommerce->cart->cart_contents_count;
?>
	<script>
                var cartCount = <?php echo $cart_count; ?>;
		var node = document.createElement("span");
		node.classList.add('cart-count');
                var textnode = document.createTextNode("<?php echo $cart_count; ?>");
                node.appendChild(textnode);
		const menu = document.querySelector("#primary-menu li:nth-last-of-type(1)").appendChild(node);
	</script>

	<style>.cart-count{width:20px;height:20px;text-align: center;position:absolute; background: red; border-radius: 50%; color:#fff; top:0; right:-15px;}</style>
 
<?php
}

add_action( 'wp_footer', 'add_number_of_cart_items' );