I have no idea where to find firmware version. Please provide explicit instructions. Apple System Profiler should provide the answer. Look for Boot ROM version; that's the same as firmware version.
Jon
macOS 11.7.10, iMac Retina 5K 27-inch, late 2014, 3.5 GHz Intel Core i5, 1 TB fusion drive, 16 GB RAM, Epson SureColor P600, Photoshop CC, Lightroom CC, MS Office 365
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