usb superdrive

As we don't know which of the 24 years of iMacs you have, I can only suggest a trick that worked on older models. Restart the computer while holding the mouse button down. A wired moue is best for this.

If that does not work, you will probably have to find a computer that recognizes the drive and use that to eject the disk.

If you fill in some details on iMac sub-model, macOS version, any warmings or advisories you see, and confirm this is an Apple superdrive and not some other brand, maybe we can offer more. It's hard to answer with almost no info in a venue where helpers can neither see nor remotely access you computer. Right now you have us guessing, and most of the senior helpers are just that —seniors. We don't guess as well as we did 50 years ago!

Terminal is an app which can be found in the Utilities folder which is inside the Applications folder. When you run Terminal you get a very basic looking command line interface, just type drutil eject external , and press enter. You can close Terminal afterwards.

Try this.

Open Terminal and type in "drutil eject external
" then press enter