Standard media players and converters usually do not support proprietary video formats and you have to rely on software provided by the company for playback and conversion of this video format. As for the n3r to mp4 conversion, it looks like that the WV-ASM200 software from Panasonic should offer conversion option for .n3r videos to standard MPEG-4 video format (.mp4).
Open N3R file Open MP4 filei-PRO Management software for several Panasonic devices