If you open the G-code file under edit on the main screen and hit the find and change all put in find G3 and replace with G2 and it will change all of the lines in the code
that have the G3 in it to G2 then save the code and exit and it will load the file back to Mach3...
I dont know mastercam codes so you will have to check to see if there are any other files that go with the G3 in mastercam to change..
That will only change the G3 to what you want , And also I am not sure if the G2 is the correct code you are looking for ..So try it out and run without
the motors engaged before you cut .
My 2 nickles worth (inflation)
Gary