Add custom fields in admin mail

Hi,

I’ve made some net fields in the checkout manager under the ‘billing’ section. The fields that i have created are named: billing_wooccm11, billing_wooccm12, billing_wooccm13.
Now when the customer orders an someting on the site the admin gets an mail.
I was wondering how can i add the fields that i’ve added in the ‘admin-new-order’ mail?

Thank you.

Greetings.

Rogier

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