Your conception is problably wrong.
Following your lojik the 3 dimension space (from a 2 dimensional view) would be like (idk, but wrong
)
It possibly like a space where the time can go forward and backward.
Or even like the dimension scheme. So, on it they have Future & "Past", and X & "Y" (like a "vertical line for time")
"Past" cause they probably wont have this concept (we dont have a concept for "front horizontal" and "back horizontal", only horizontal).
I hope that everyone can understand what I mean.