When configuring JetBackup, the Blackblaze Destination type is not available.
Check which version of JetBackup is installed. Version 5 does not have Blackblaze as an available destination type.
Their documentation explains more of the differences between versions 4 and 5.
The only means to utilize a Blackblaze backup destination type is to reinstall with JetBackup version 4, presuming it is suitable for the OS environment.