I have an older Mac from 2010 (all in one monitor and computer) with no operating system on it. I have been trying to redownload the OS through USB but have had no luck. System recognizes the flash drive and the OS but I can’t get it to run. Disk drive is not an option. There is no data on the Mac that I need to save, just want it to run. Probably looking at a Sierra, high Sierra, or maybe Catalina.
Earlier Mac models
Without specific info about your Mac, we can only guess at the appropriate response.
Enter the serial number of the Mac here: Check Your Service and Support Coverage - Apple Support
and then tell us the model and year of the computer.
Why is "Disk drive...not an option"?
How did you install an OS onto the flash drive?
Please see: Create a bootable installer for macOS - Apple Support
Have you tried to boot the Mac in Recovery mode?
You may be able to reinstall the OS if the Mac can reboot into Recovery.
Please see: Use macOS Recovery on an Intel-based Mac - Apple Support
High Sierra would be tops for a 2010 iMac...
macOS High Sierra - Technical Specifications
General Requirements
Mac Hardware Requirements
For details about your Mac model, click the Apple icon at the top left of your screen, choose About This Mac. These Mac models are compatible with macOS High Sierra:
macOS High Sierra - Technical Specifications
https://itunes.apple.com/app/macos-high-sierra/id1246284741?mt=12
Operating System
