I accidentally reset my MacBook Pro without a backup

Here is an Apple article with instructions when encountering the screen with the circle with a line through it (or prohibition symbol):

If your Mac starts up to a circle with a line through it - Apple Support

gevork240 Said:

"I accidentally reset my MacBook Pro without a backup: i completely deleted and reset my 2011 MacBook Pro without a backup and now I can’t reinstall anything. I’m left with a white screen"

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Thank you for the photo.

Mount the Hard Drive in Disk Utilities:

Boot in to Recovery Mode (Hold Down [command+R] when you hear the boot chime). While booted into Recovery Mode, go to Disk Utility> tap the Hard Drive, then tap the Mount button. See if you can then install it. If it is already mounted, then unmount it and then remount it. See where you can go from there.