How to find my old registration code?

[RoxasXIIIkeys]

Hi, I purchased VideoPad Video Editor years ago back in 2016, and even had a registration code. And this year, my video editor has been endlessly lagging and loading like crazy, and I realized that the version I had was v4.58 and I looked up what the latest version was and it's v10.27, so it turns out I've been using an outdated version for so long and the video editor itself NEVER gave me the option to update the software. So I decided to download the latest version, however, it's asking me for a registration code if I already purchased it, but the issue is that I don't remember what my registration code was nor do I know how to find it anymore, and I don't want to have to purchase it all over again all because I had an outdated version that refused to update.