The PRJ extension is attached to project files created with 3D Studio, the predecessor of 3ds Max, created for operation on the DOS platform. PRJ is also known as a mesh file, containing graphical data related to geometry, texture, lighting and other relevant info associated to a 3D model.
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 PRJ 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 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 STL APNG DDS SVGZ CG4 FLIF