You have a long procedure in front of you. Those versions are several years old and unfortunately upgrades of the DC need to be done sequentially. A sensor can be re-imaged directly to a new version and then re-registered to the manager and policies reapplied but that requires an non-trivial outage which may be unacceptable in production. So often it also needs to be upgraded sequentially as well.
Defense Center is the old name from Sourcefire. Cisco first called it Firesight Management Center and then later switched to Firepower Management Center.
The path you need to follow is laid out here:
https://www.cisco.com/c/en/us/td/docs/security/firepower/620/relnotes/Firepower_System_Release_Notes_Version_620/important_update_notes.html#id_38002
In short, it is Version 5.4.1.1+ > Version 6.0.0 PreInstallation Package > Version 6.0.0 > Version 6.0.1 Preinstall > Version 6.0.1 > Version 6.1.0 PreInstallation Package > Version 6.1.0 > Version 6.2.3 > Version 6.2.3.2 (current latest patch).
Once you get FMC to 6.1.0 you will also need to upgrade the 3D8350 appliance(s) to that release. That's because 6.2+ FMC can only manage 6.1 and later devices. In all cases, your FMC must be at or above the release of the managed devices.
