laborious drive – Re-partition with out damaging backup set

I’ve an eight-terabyte powered drive formatted as follows:

/dev/disk12 (exterior, bodily):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *8.0 TB     disk12
   1:                        EFI EFI                     209.7 MB   disk12s1
   2:                  Apple_HFS Seagate 3TB             3.0 TB     disk12s2
                    (free area)                         134.2 MB   -
   3:                 Apple_APFS Container disk13        5.0 TB     disk12s3

/dev/disk13 (synthesized):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      APFS Container Scheme -                      +5.0 TB     disk13
                                 Bodily Retailer disk12s3
   1:                APFS Quantity Seagate 5TB             4.0 TB     disk13s2

“Seagate 5TB” is a Time Machine backup drive.  “Seagate 3TB” is empty aside from .DS_Store,.Highlight-V100, & .fseventsd that are meaningless on an in any other case empty quantity.

If doable, how can I convert it right into a single APFS quantity with one container and two volumes, merging 3TB and the free area into one quantity, with 5TB the opposite quantity, with out breaking the backups already in 5TB?

If needed (and doable), I might copy the backup set to an empty 5TB bodily drive and replica it again.  However I’d reasonably not, as a result of that may take a LONG time (5TB is already 4TB used).

I feel I might additionally have to set quotas, to alter 5TB to six TB or much less and 3TB to 2 TB or much less (renaming each).

I don’t belief the AI-generated reply that tells me to backup the backup after which erase. 🙂