Add Customers Date of Birth to all Order Confirmation eMails by silkblooms

We have a Zen Cart site where the customer enters their date of birth on registration. I need this date of bith to be included in all new order confirmation emails. At present, the the order confirmation emails only includes their name, address, email, telephone and IP… (Budget: £20-£250 GBP, Jobs: HTML, Javascript, MySQL, PHP, Website Design)