dose calibre backup use a proprietary format/compression or is it possible, with some effort, to break up a backup file using tools like winzip, winrar.. ?
-> OP . you said TIB file.
google tells me
What is a TIB file? Disk image created by Acronis True Image;
so get hold of that program and see what it can do for you
presumably you once owned that ?
https://fileinfo.com/extension/tib
unfortunately , TIB is a " true copy" aka a track by track system image of a hard drive so maybe it can only be restored to an empty(blank) spare drive.