MAC COMES ON TO THE DISK UTILITY SCREEN

No backup, huh......oooh, harsh. you might want to rethink that after you get through this.....

Usually you'd restart your Mac, Holding down Command (Apple+R) keys together to get to the Recovery Partition.....

I don't know exactly what OS you have on there, but I'm guessing it's sierra, Mavericks or even Snow Leopard.

It would be nice if you knew which OS you had, but you don't.

Otherwise, you could try Command (apple)+Option+R keys together on restart with an Ethernet cable plugged in to get to

Internet Restore.

Oh, and just to let you know. This is probably your first time posting here, but YOU DON'T NEED TO WRITE IN ALL CAPS. It's kinda

like shouting. We can read what you're saying just fine.

If your Mac Pro has a DVD drive, and you're desperate, you could use a DVD copy of Snow Leopard, and from there, update to El

Capitan which would allow you to access the App store and get the latest OS you could.....

As for the Data and stuff on your hard drive.....that's tougher. If you're in the Disk Utility screen, running disk First Aid is OK.

Clicking on "Format" is a very bad idea now.

Then you'd have to choose whatever hard disk showed up as the Startup Disk, and then OK. and reboot.

before choosing the hard disk, you should be able to get out of there, and choose "Re-install OS", which you might want to do

then choose, then OK, then restart.

Hopefully Disk Utility will be able to solve some minor problems, and you'll be able to be OK.

IF you think your hard drive is hooped (for lack of a better more polite word here) then you'd have to borrow/buy an external hard drive of some kind, appropriately formatted, and some kind of Data Rescue application. Sadly, neither of those are free, but if they work, then they may have been worth the money you spent on 'em.

You could also try restarting and holding down the Option Key on the keyboard. That will invoke the Startup Manager, which will show you all available and bootable hard drives. From there you should be able to get to the Recovery partition, and on your way

good luck to you

ps---you might want to, in future, have and use a backup system. Time machine is built into the OS. It's easy to use, reliable, and could save you a ton of grief....however, for now, the barn door is open, and the horse is starting to leave, so we have to get the horse back and the barn door secured, if you catch my drift

john b

The drive you were using is damaged. Try to use it as little as possible. Do not attempt start up from it any more, if you can avoid it. because you do not have a Trusted Backup, you will need to take extreme measures.

Obtain an unused External drive. Install a new copy of MacOS on it. (Your Mac can install and boot from any drive, Internal or External). On recent Macs with T2 chip, you may have to grant special permission to boot from an external drive

This gets your Mac sort of working again, and takes some of the pressure off. It also allows you to use the full power of a working MacOS and additional programs to 'salvage' some data off the old drive.

General-purpose 'Data Rescue' from Prosoft can make excursions onto the damaged drive and try to find your files. There are several others that are tuned to finding Videos or Photos.

Don't waste your time trying to make an exact replica of the old drive. Remember that over 350,000 files are MacOS, which can be re-installed exactly as before quite easily. Your files are likely to be far fewer. Focus or rescuing your files.