Question: time machine backup to portable USB
I have WD my passport portable external USB as one of my backup disks (in addition to time capsule).
Due to various changes such as old Mac vs. new Mac; El Capitan vs. Sierra vs. High Sierra etc., now the backup disk shows its content as per attached 1st SS. The highlighted folder is what I'd like to keep/continue with the backup, since it contains more of the earliest backups than the other folder seen. In addition, there was another backup folder which was backed up from the time I purchased this new Mac. But since I kept getting 'no space' errors on time machine, I sent it to trash (2nd SS).
How do I get the new Mac to continue using the older backup folder (1st SS)? How can I also get the folder that is currently in trash (2nd SS) also merged into the backup folder so that all backups would be available?
MacBook Pro (15-inch, Late 2016), macOS High Sierra (10.13.3), Time Capsule 1 TB (1st Generation)