I AM ABOUT TO CRY STREED WITH THIS PROGRAM…any body can help to get my serial number
If you truly have a Classic license with a serial number it can be found here: Help > License. However if you have a subscription the case is different.
You have a subscription, and it is assigned to the same email address you use in the forum. When you open SketchUp, sign in using that email address, and SketchUp will work. You do not need to look at the Classic part of the license screen.