There is one way you can get image file from windows exe file. Follow below step to get image file and try to update through GUI 
I am in need of updating server iDRAC card's firmware to 1.65 and the ways to do so now are updates which require you to run them on the host OS which has to be windows or Linux. I have two servers which do not have OS's on them so I can not update in this manner and it is silly for me to install or run an OS on each of these just to install a firmware update for the DRAC card. I also have four other machines where the windows exe is not updating the card because as it begins the update it fails saying the card is not there even though before it was told to move forward with the update, it identified the card and its version of firmware.   I did reference this thread already [URL] and the person who asked where they could get the image was never answered and I could really use the image to resolve my problems.  Thank you for your help.  Thank you 
Updating iDRAC firmware for M600 with image