Is there any way to convert a .dmg file to a .iso or any other relevant format, such as .daa etc.?
Ultra iso has support for many image file types, Link below
I think it's Shareware/Trialware
Ohterwise download isobuster below and select file menu and open your .dmg file. then right click the image in left hand pane to see if it will allow you to convert.
hope this helps