I want to know the file name which is responsible for sending the order details to the customer after purchasing product in virtuemart. I have searched a lot but couldn't find anything.
After a customer purchases a product from your store, the order details are saved in the "orders" database table. You can edit this table to change the order details such as the order status, customer notes, etc.
If you want to edit the order details after a product has been purchased, you need to edit the file "components/com_virtuemart/views/invoice/tmpl/order_status.php".