Woocommerce get custom select fields value at thank you page

I am using woocommerce plugin and i want to add custom select field at the checkout page. I added a function and hook to function.php page. It’s displaying at the checkout page. But how can i get the value of that field in the thankyou.php page.

add_action('woocommerce_after_order_notes', 'my_custom_checkout_field');

function my_custom_checkout_field($checkout) {
    echo '<div id="my_custom_checkout_field"><h3>'
        . __('Select Where Your Points Go') . '</h3>';

    woocommerce_form_field(
        'points_go_to', array(
            'type'     => 'select',
            'class'    => array('form-row-wide'),
            'required' => true,
            'label'    => __('Select a Side'),
            'options'  => array(
                'dfault' => __('Default1', 'woocommerce'),
                'left'   => __('Left Side', 'woocommerce'),
                'right'  => __('Right Side', 'woocommerce')
            )
        ),
        $checkout->get_value('points_go_to')
    );

    echo '</div>';
}

I tried to get the points_to_go field value in this way. But it did not work.

$checkout->get_points_go_to();

I have these values and how to derive side value.

["_side"]=> array(1) { [0]=> string(6) "dfault" } ["_shipping_country"]=> array(1) {   
[0]=> string(2) "LK" } ["_shipping_first_name"]=> array(1) { [0]=> string(7) "saman"
} ["_shipping_last_name"]=> array(1) { [0]=> string(11) "perera" }