What do I do if I accidentally erased Mac OS
I accidentally removed the Mac OS off my computer and now I only have a folder with question mark
Follow the instructions here: If your Mac starts up to a question mark - Apple Support
First read all the blue links on the above linked page to familiar yourself with what the various screens mean and what to choose.
Then you will start with Turn on your Mac and immediately press and hold Command (⌘) and R to start up from macOS Recovery.
You will be installing MacOS and this takes quite awhile to complete. Then you will set it up again.
Have a good internet connection and your Apple ID handy
