I bought my GSX, but when I look for the serial to activate it. it says that there's no order in for my email.
You must have confused the activation methods. The one that asks for your email+serial number, which is called the server-assisted Reinstall, can't be used for Web orders, only for the direct purchase from FSX.
To activate your Serial Number for a Web purchase, you must use the "Register Serial" function on the Addon Manager, and that one will NOT check your email, it only needs your SERIAL NUMBER, which is found in the purchase receipt that you received by email.
Also there's no confirmation when I bought it in my PAY PAL.
You mean you haven't got a purchase receipt from PayPal ? If you go into your PayPal account, there's no transaction ? If this is the case, then you haven't purchased anything yet, which also explains why you haven't got a purchase receipt with a Serial Number too.