iMac was wiped, no more Macintosh HD

Hi Lana-stuffed-up,

Thanks for posting the screenshot! It looks like the internal drive might have been erased, but not reformatted for Mac use. Complete these steps to reformat your drive and reinstall macOS:

1. Start up from Internet Recovery: Hold down Option-Command-R as you power on or restart your Intel-based Mac.
2. If you're asked to authenticate with admin credentials, complete these steps instead: How To Fully Erase A Mac Using Recovery A… - Apple Community
3. When the list of utilities appears, choose Disk Utility and continue.
4. In Disk Utility, if a View button appears, click on it, then choose "Show All Devices".
5. Select the top level of your internal drive (APPLE HDD) and choose Erase. Select these options, then click Erase:
   1. Name: Macintosh HD
   2. Format: APFS, or Mac OS (OS X) Extended Journaled
   3. Scheme: GUID Partition Table/Map
6. When the reformat is complete, quit Disk Utility.
7. The list of utilities should reappear. Choose Install macOS (or Install OS X) and continue.
8. Complete the onscreen instructions to reinstall macOS.

If an error appears in the macOS installer and you can't proceed, please provide the year and model of your iMac. This info helps significantly for finding other solutions to reinstall macOS.

To get the year and model of your iMac, provide your serial number to Apple's warranty coverage site: Check Your Service and Support Coverage - Apple Support

To find your serial number: Identify your iMac model - Apple Support (CA)

Startup in MacOS Recovery and select Disk Utility, then Erase and Format the Apple HDD

as per > Use Disk Utility to erase an Intel-based Mac - Apple Support

Then go back to the Recovery Utility screen and select Reinstall macOS

as per > How to reinstall macOS - Apple Support

Restoring your Mac to factory settings involves reinstalling the macOS software while booted in Recovery mode. 

This is Apple's guidance on how to do that:

How to reinstall macOS - Apple Support