How to add new fields on order confirmation and send them to email in opencart?

Question

PHP

Hello, I installed a boxberry delivery widget on opencart 2.3. I want the data about the selected delivery terminal and cost to be sent by e-mail when placing an order.
The Simple One Page Checkout module is used.
I added two hidden inputs to shipping_method.tpl and using JS I add delivery data to them.
But here's how to transfer the data further, which files to edit in the controller so that the data from these inputs falls to the administrator's mail when ordering?