https://docs.appeon.com/pb/upgrading_pb_apps/
Start with the section for version 12.5 and work you way up through all of the subsequent versions so that you can be made aware of all that has changed in PB since version 12.5.
If your app is based on a framework (such as STD or PFC, for example), you should update the framework's libraries with the latest versions.
If you will be upgrading in order to produce a 64-bit PB app, I strongly recommend that you first successfully upgrade your application while leaving it as a 32-bit app. Once you have thoroughly tested and verified all is well, only then should you consider converting the app to 64-bit. There is also a publication that will help you with that:
https://docs.appeon.com/pb2022r3/migrating_32bit_applications_to_64bit/index.html
Good luck and best regards, John