If you would like to confirm that you have received a purchase order, here is a sample template you can use to write an acknowledgment letter against a purchase order.
To [Recipient name]
Dear, [Recipient name]
This is to inform you that the purchase order of [Product] has been received on [Date]. We are satisfied with the speedy service and appreciate the quick delivery of the purchase order.
The outstanding amount, if any, will be paid to your bank account number [Number] by [Date]. The order was delivered in a presentable manner. We wish to continue doing business with you in the future.
Thank you for your efficient services.