Restore both macOS and your files
These steps erase your hard disk, then use your backup to restore both your files and the specific version of macOS you were using when you created the backup.
Make sure that your Time Machine backup disk is connected and turned on.
If your backup disk isn't available, keep going: You might be able to restore from a local snapshot on your startup disk.Turn on your Mac, then immediately press and hold Command (⌘)-R to start up from macOS Recovery. Release the keys when you see the Apple logo or spinning globe.
When you see the macOS Utilities window, choose the option to restore from a Time Machine Backup.
Click Continue until you're asked to select a restore source, then select your Time Machine backup disk. Or select your startup disk (Macintosh HD), which might have a local snapshot you can restore from.
Click Continue. If your disk is encrypted, you're asked to unlock the disk: Enter the administrator password you used when setting up Time Machine, then click Continue again.
Select a backup, if available, then click Continue.
Select a destination disk, which will receive the contents of your backup. If restoring from a local snapshot, you aren't asked to select a destination.
Click Restore or Continue. If your Mac has FileVault turned on, you're asked to enter your administrator password to unlock the disk.
When done, restart your Mac.
