You need 3 noncollinear points to define a plane. To be noncollinear, it means to not fall on the same line.
Points S, Q, and N are inside of plane R. In other words, they appear to lie on the flat sheet of paper that composes the plane. So we can label this plane as "plane SQN". The order of the letters does not matter. We can pick any three points that are inside this plane as long as they do not fall on the same line.
Note: points Q, N, and O appear to fall on the same line (though it's hard to confirm), so it might be a bad choice to pick these three letters.