If you have the lastest update, adobe should be able to open mfx files. If it can’t for some reason you can go 2 routes.
1. buy the prospectHD codec that rewraps the data to intraframe without any transcoding loss
2. use free ffmpeg and transcode to a similar bitrate and chroma codec like dnxhd or dvc pro hd etc.
FFmpeg can create D-10 MXF files and XDCAM HD 422 files compatible with Avid Media Composer and “import” into bin feature.
also…
Before you can copy the files from the fs100, you must go to the “Utilities” page (on the firestore unit) and select “Organize P2”. The fs100 will then correctly organize the footage (along with the audio) into the folders compatible with what Premiere cs3 recognizes as a DVCPROHD P2 file (contents, video, audio, voice, proxy…). After this, just copy the “Contents” folder onto your pc hard drive and import it in premiere.