touché. But none of those are useful in this situation. Or they are. Dunno. I don't use them.
Wavefront OBJ: Exports as an .obj that most modeling programs can open.
To fix that triangulation, I suggest selecting faces with triangulation,
(Go to the selection tool and fit the faces button) and weld them together. It removing the flatshading on the particular face hiding any triangulation.
It's how Baddy hid triangulation on the Blockhead minifig.