functions.php

function custom_tracking_code() {
    if ( is_product() ) {
    ?> Add your Product code here <?php
    } elseif ( is_cart() ) { 
    ?> Add your Cart code here <?php
    } elseif ( is_order_received_page() ) {
    ?> Add your Thank you code here <?php
    }
}
add_action( 'wp_head', 'custom_tracking_code' );