I can backup my mac before reinstall mocs
i connected the USB but I don’t see anything to backup
MacBook Pro 13″, macOS 10.12
In this picture above - Time Machine Backup is waiting for the User to choose the Drive to be used for the TM Backup.
In the the link >> Back up your Mac with Time Machine << it will explain how to setup TM Backup and the choice of Drive to be used. Make sure the external drive is formatted as HFS Journaled and GUID Partition Map for it to work properly.