Are you currently trying to to a specific iOS version, or are you just trying to unbrick the device?

: This means the software on your computer (typically iTunes or Finder) is unable to locate or send the necessary bootloader file (the code that tells the phone how to start the operating system) to the device. Common Causes

I’m trying to work with an (which I believe is the iPhone 7, model number 3D101AP ), but I keep getting the error:

If you are stuck and need to get your iPhone 7 back to a working state: