Hello Lylex,
You can delete (i'm sorry this is too late) jobs and volumes for the old servers using the purge command from bconsole. The pools (if they were only used by the old servers and you are not going to use them anymore) should be deleted using the delete command from bconsole and removing their definitions from the bacula-dir.conf (or whatever conf file you have your pools definitions).
If you have your pools configured to automatic labeling volumes, then they will be created on demand. Otherwise, you must explicitly create them using bconsole/label command.
Best regards,
Ana