Help Saving a Time Machine back up file

Sorry if this is a really basic question but I could not find an answer anywhere. I am trying to save a time machine backup file to another disc. The current one is not repairable but the file can be read and copied. I am trying to do a simple copy to another disc and I keep getting a message that the destination disk "is not formatted for a backup". I don't want to perform a back up or restore..... I just want to save the file as is. It is almost 1TB file. any suggestions ? It contains about 3 years of time machine backups.

All of my drivers are formatted as "Mac OS Extended (Journaled). Not sure what the formatting problem is. I feel like the system is acting as if I need to set the disc up as another Time Machine, but again- I just want a carbon copy of the backup file in case I ever need it.