PNM (Portable Anymap) is a generic format for the Netpbm pack, consisting of intermediary files used in the conversion process by a collection of open source programs called Portable Bitmap Utilities. PNM is used as a generic name for the 3 file formats which are part of this pack: PBM (Portable Bitmap), PPM (Portable Pixelmap) and PGM (Portable Graymap).
The quick and simple way to handle your files is to get a quality piece of software, such as reaConverter. This software is extremely efficient in managing a wide range of batch conversions. As you will soon realize, reaConverter will help you avoid spending countless hours trying to figure out how to convert multiple PNM files as once.
JPEG JPG PNG GIF TIFF TIF BMP ICO EMF WMF AI PDF EPS PS EPI WEBP WEBPLL JP2 PCX TGA DWG DWF DXF DGN WMZ CGM DRW SHP GBR PCT MIF PLT PCL SVG WPG CIN DCX DIS HRU MTV PRC RAD PIC RLA QRT SGI XBM XPM SWF CAL FAX FITS PSD PGM JXR BPG APNG DDS SVGZ CG4 FLIF AVIF