Hi Solace,
welcome to this forum 🙂
to give you some background info for better understanding in the future:
the file extension".mov" is a bit irritating, should NOT be translated with "movie"! a .mov is just a socalled container, it can contain (sic) many kind of media: stills, music, VR...- and for sure video.
just to impress you, have a look in this list:
Apple's list of formats supported by QT
iMovie is an edit-app meant to work with firewire-connected miniDV camcorders..... you
can import "other" files&formats, but then it gets a bit tricky....
so, my usual guess, you're trying to import some mpegs (contained in a .mov file, you don't read .mpg as suffix.....)
some very good advices here, in plain english:
http://danslagle.com/mac/iMovie/tips_tricks/6010.shtml
http://danslagle.com/mac/iMovie/tips_tricks/6018.shtml
have fun with your Mac! 🙂