When you upgrade macOS or migrate content to a new Mac, software known to be incompatible with the new macOS is set aside and won’t run on your updated system. This incompatible software might be relocated to a folder in /Users/Shared/Relocated Items/, or to a folder at the top level of your Mac startup disk.
If you want to use one of the incompatible apps, get an updated version that's compatible with your new operating system. Apps in the Mac App Store list their compatibility and system requirements on their product pages. You can also check with the app developer to find out if they have a new, compatible version or plan to release one.