Where is the file in WooCommerce where form data is sent when an order is confirmed?

Question

WordPress

Hello! I don’t deal with websites often, so I don’t have much experience, and in WordPress I’m generally making a website (online store) for the first time. Before, I just tinkered with it a little. Therefore, many terms familiar to WordPress developers are not familiar to me.
The task is as follows: when confirming an order, it is necessary to send data from the form to Bitrix24 CRM to create a new lead. I understand how to do it. You just need to send data from the form using the POST method to CRM using AJAX (I already did this but on the landing page). I imagine the implementation like this: I click on the "Confirm order" button (on the checkout page) and everything goes where it needs to. But the problem is that I can't find the php document that is called when this button is clicked ("Confirm order"). In Chrome, it shows that the document is called along the checkout path. That is, the document on the page of which I am (as I understand it). Please help me realize what I have planned. It is necessary to implement this exactly when you click on the "Confirm order" button.
Thanks in advance to everyone who has shown interest in this issue.

Answer 1

No need for AJAX here.
Add function to woocommerce_checkout_update_order_meta action