To start up your Mac correctly, you need to reinstall macOS.
The presence of the folder with a question mark shows that your Mac doesn't have a working operating system, which is caused by you erasing the startup disk. So the solution is to acquire a new macOS. To make sure that you format your startup disk correctly, follow the steps below to reformat your Mac again and then reinstall macOS.
- Close Disk Utility if you're still on the window.
- Click the Apple logo and turn off your Mac.
- Wait for it to shut down completely.
- Hit the power button, then immediately press and hold the Option + Command + R keys until seeing the spinning globe.
- In the macOS Utilities menu, check which macOS you can reinstall.
- Click Disk Utility > Continue.
- Click View > Show All Devices if available.
- Select the drive (248 D6 GB P4 243 media in your case) and click Erase.
- Name the drive Macintosh HD.
- Keep the default format. (Should be APFS if you're reinstalling macOS 10.13 or later.)
- Keep the scheme GUID Partition Map.
- Click Erase.
- Exit Disk Utility.
- Click "Reinstall macOS" and Continue.
- Follow the onscreen instructions to reinstall macOS.
