Woocommerce - 在Checkout中获取自定义字段的价值

I have a nimble question that i am not getting any answer of. I have added a custom field using "Checkout Field Editor" in Woocommerce Checkout fields. The field is given below and seems to be working fine.

 <input class="input-text " name="wc_order_field_7542" id="wc_order_field_7542" placeholder="Pickup Date" value="" type="text">

However, now I am working on a plugin and want to get value inputted in this specific field and cannot seem to figure out. For the other fields I am simply doing the following as I am doing for "billing email" and it is working:

public function get_billing_email() {
        $billing_email = $this->order->billing_email;
        return apply_filters( 'xc_woo_cloud_print_billing_email', $billing_email, $this );
    }
public function billing_email() {
    echo $this->get_billing_email();
}

I am sure I am forgetting something and not doing something right.

Any help is appreciated.