Probably more difficult than it sounds. If it was one object you could centre it on screen using
set position to
x=(ViewportLeft(0) + ViewportRight(0))/2
y=(ViewportTop(0) + ViewportBottom(0))/2
You could create a sprite, when all the squares are in position, pin them to this sprite. Then use the calculation above on that sprite, then everything would be in the centre of the screen. Depends what your game does really.