“Please confirm upon receipt” is the correct sentence. This sentence is asking the recipient to tell the person who sent the item to confirm or tell them that they have received the item.
Means: “kindly, acknowledge receipt of this email” or “Please confirm receipt”.
It is often used in letters and emails.
Below is a short email as an example:
I am emailing you to let you know that I have sent the parcel to your office.
Kindly confirm upon receipt.
In the email above, Marie is asking John to tell her when the parcel arrives at his office.