i have a couple dreamcast games. i was wondering if there is a way i can put them into my computer(mac) and use a software or something to convert them into .cdi images. Thanks for the help in advance

Firstly, you want to create GDI files, not CDI, for GD-Rom images.

Secondly, it's unclear whether or not I can tell you how to create the images, even if it's perfectly legal for you to format-shift the media that you own, so I will just say that programs and instructions to do this are available elsewhere on the net.