prj to avi conversion can be pretty much any kind of 'project' to video export, ranging from video editors to renders of 3D models. Unless you know exact origin of your 'project' file, it will be almost impossible to determine what software to use. But generally speaking, projects are tied to the original software only and very rarely can be opened/imported to 3rd party software, so you need specific program for specific .prj file.
Updated: September 14, 2023