Converting a .ev3p file into a .ev3 project file
Actually, you can't convert a .ev3p file into a .ev3 file. Based on this post and other ones here's what a .ev3p file really is:


  When you unzip a .ev3 program, there are many txt and xml files that are inside. In particular, there is an xml file produced with the filename extension .ev3p, which contains program instructions that the EV3 brick can then interpret and execute.


So now we can conclude that a .ev3p file is only a certain part of the .ev3 file.