You can create an order confirmation in two ways. Option A is to make the order confirmation complete from scratch . Option B is to create the order confirmation from an existing invoice. Both possibilities are described below.
Option A: On your dashboard, Click on plus sign > create order confirmation OR Go to sales > order confirmation
Now fill in all (mandatory) data, so that you can send the order confirmation and print it out to inform your customer that the order is being processed.
Option B: Go to the invoice for which you want to make an order confirmation by going to sales > invoice from the menu item.
click on Action > create order confirmation
This way you can create a different document type directly from a specific document.