how do you back up mac book that isnt working

Backups have to occur before the backups are needed, whether due to loss, failure, theft, dunking, corruption, or whatever.

Target disk mode might get access to your data from another Mac, but that’s doubtful.

Transfer files between two Mac computers using target disk mode - Apple Support

Telling people to backup is a standard recommendation used in all sorts of instances for obvious reasons. If your machine is damaged to the point it can't be used, then you have to rely on the last backup you made. And for Time Machine, that's on an external disk you don't send along as part of a repair.

If you have no backups, you may be able to access the data some other way. Remove the drive if that's possible, use Target Disk Mode if available. Everywhere you read concerning Mac usage, you'll find references on the need for backups for the exact condition you have currently. And those always deal with backups before failure as an "insurance policy".

LisaCr027B wrote:

I have to send it in for repair because its not turning on , so it has auto backups but going through the list of what i need to do to send in for repair it says back up then remove from find my iphone etc so that they can access it to fix it.

as its totally dead i cant do anything on the actual machine - just wondered if there was a way through icloud.

Your data is quite possibly already gone.

Given this Mac is bricked, you have no options.

Target Disk Mode might get you access, but that depends on a semi-working Mac and this Mac seems bricked.

iCloud is not used for Mac backups.

If you did use iCloud Drive for your desktop, you might have your files there.

But there’s no go-back-in-time-and-perform-a-backup option.

Time Machine or other backups have to happen prior to the failure/loss/theft/damage/dunking.

One other thing. Your data may be preserved on your Mac. Unless the drive is damaged, the repair may not even affect it.

My 2016 MBP ( was my son's) needed a new logic board and I assumed his data was gone. I was surprised to find all his data intact when I got the Mac back.

Backups are safety nets, it does no good to erect a safety after you fall off the cliff