In order for FCP to read MXF files you need:
(1) The correct plugin installed from whichever camera manufacturer is producing your flavor of MXF.
(2) The entire card copied over exactly as it appears on the card. The entire folder structure must stay in tact or everything goes south. You cannot copy over just the MXF files. The folders, XML, and MXF files need to be kept in tact.
Adobe Premiere Pro can usually read the files without the card structure. You could download the free 30-day trial, ingest the clips, and export them as ProRes if necessary
Ryan Holmes
http://www.ryanholmes.me
@CutColorPost