https://stackoverflow.com/questions/18533567/how-to-extract-or-unpack-an-ab-file-android-backup-file
Install Android Backup Toolkit
wget https://downloads.sourceforge.net/project/adbextractor/android-backup-tookit-20180521.zip unzip android-backup-tookit-20180521.zip cd android-backup-tookit/android-backup-extractor/android-backup-extractor-20180521-bin
Unpack backup. Changes it from an ab to a tar file
java -jar abe.jar unpack ~/path/to/backup.ab ~/path/to/backup.tar
After thats complete, you can untar it. Change Desktop to the path you want to extract to.
tar -xvf ~/path/to/backup.tar -C ~/Desktop/