this will need some steps, it cannot be done in one step.
first you will have to migrate your backupexec version to the new windows server.
once done you can upgrade your backupexec to the newer version. following the upgrade procedures from Veritas
As BE 2012 probably won't install on Windows 2016, you may have to look at using BEMIG (As I am not sure BE 16 will run on 2008 SP2 as I think the lowest version of BE 16 will install on is 2008 R2 x64)