Firefox browser isn't a email program.

If you created the order on a website, but did not complete your transaction, the order might be in your shopping cart or basket on the site. Some sites will even email you to try to get you to complete the purchase.

But your question is kind of unclear on where you are in the process. Are you trying to return to the website? If you have trouble remembering the address, check your history. Either:

• menu button > History
• Ctrl+H to open the History sidebar
• Ctrl+Shift+H to open the Library window

If you are trying to find an old email, usually each email site has a method to search in your messages. But exactly how you do that depends on the site.