You can have a look to the backup, restore scripts to check how they work.
On my system the environment variable
OPENHAB_BACKUPS=/var/lib/openhab2/backups
is set.
Backups are stored in that directory and taken from there.
According to the usage of restore:
usr/share/openhab2/runtime/bin/restore -h
##########################################
openHAB 2.x.x restore script
##########################################
Usage: restore filename
e.g. ./restore myBackup.zip << Restores config from myBackup.zip
Use this script to restore an openHAB configuration that was previously made with
the openHAB 'backup' script.
you even can directly call/start the restore script and use the zip file as an argument.