I need an itemized receipt of my Apple Watch purchase

We are all users on this user to user only forum. We don't know you, know where you purchased your watch exactly and have no access to purchase details. If you bought your watch from Apple directly, you should have received an email with the purchase details. You can visit the store you purchased the watch from. Or if you did buy from Apple, you can open the Apple Store app (not the App Store app) and check your purchase history, by taping the search button on the bottom, then My order status to see your purchases.

If you bought it from apple then;

https://secure4.store.apple.com/in/shop/order/list

Or;

Go to reportaproblem.apple.com. Sign in with your Apple ID and password. A list of your recent purchases appears. From here, you can view a receipt, request a refund, or report a problem with an item

Or;

You would want to contact Apple Store on the phone and ask them to email copy of the receipt to you again. You will have to verify yourself by providing some transaction details and you will want to verify precise spelling of your email. Phone number can be found at www.Apple.com/retail