Extracting individual images from your MP4 files is quite easy with the FFmpeg utility. You may already have it installed on your Linux or MacOS system.
Say you have a video file called MY_VIDEO_FILE.MP4:
ffmpeg -i MY_VIDEO_FILE.MP4 frame%04d.jpg -hide_banner
This will extract the individual images in the same directory as follows:
frame0001.jpg
frame0002.jpg
... and so on ...