Following up on what Dameon said, both ways should be fairly easy, but when I do upgrades such as a big one like this I prefer start fresh and clean. If you have access to a lab then you should be able to compare the two different ways(It's a great way to practice and also vet any issues that might arise)
1) Do a migrate export of your current R77.30 management server
2) Migrate import into a new R77.30 management server that's in your lab
From here you can either do an in-place upgrade or use the R80.x upgrade tools and export the database to a fresh install of R80.x
Good luck Anuj!