Go to the product pages at https://www.vegascreativesoftware.com/us/vegas-edit/ (click the globe button at the top bar of that page to select your area and see the page that applies to you, Scroll down the page to the Online Shop and see if your previous serial number is valid for the upgrade pricing. If not, you need to purchase a new license to get the latest version.

@adiel-Yisrael