MP4 isn't a Final Cut compatible codec. ProRes is.
Typically you would use Log and Transfer to bring in this footage. Here's a tutorial on how to do that.
However, some newer cameras aren't compatible with FCP 7...they might shoot a format it doesn't work with, like 1080p60. For that, you need ClipWrap2 from divergentmedia.com. And convert to ProRes 422.