gray folder with question mark - erased hard drive - nothing working

I’m not positive that I have the correct model of iMac listed. This is an older iMac that I purchased from a friend. I’m pretty sure it’s 2009 though.

I tried to erase the hard drive so that I could start with a clean computer. After erasing the HD, I tried reinstalling OS. When I chose “Reinstall” from disk utility and clicked “Continue” nothing would happen.

So I did a hard restart. That’s when the gray folder with question mark appeared. I have tried resetting the PRAM, CTL+CMD+R, Option… pretty much every suggestion I could find. Who knows what I’ve done at this point.

I’ve restarted my computer about 20 times. Unplugged it and let it sit, etc. Everything brings me back to the gray file with a question mark (except OPT on restart which gives me a plain gray screen)

This is too large of a paperweight for my small desk. PLEASE HELP!