How do I upgrade Wondershare Video Converter 2 to the Catalina system?

Look for upgrades from the developer. Nothing we can do to help with that. See App Compatibility Table - RoaringApps.

Please read Writing an effective Apple Support Communities question. We are here to help. We are all users. We are not mind-readers nor clairvoyants. We only know what you write down and tell us. Be specific and thorough. Include your hardware information and installed version of macOS.

FYI: These are user-only forums. You are not speaking to Apple. if you need to speak with Apple Support, then contact product and tech support:  Contacting Apple for support and service including international calling numbers.

Thank you for your understanding and support.