Ok, this is going to take a bit of explaining.
First, when you compile all the maps are compiled into one map. So Test1.dmp and Test2.dmp are now one map.
When they are compiled they are placed on top of each other in alphabetical order.
I'm not sure if you understand what Z level's are, I'll explain them briefly just in case you don't.
Every tile on the map has 3 co-ordinates, X, Y and Z. X is how far away it is from the WEST border of the map, Y is how far away it is from the SOUTH border of the map, and Z is what level map it is on.
We can add new Z level's two ways, first by adding more *.dmp's. Second, by adding new ones to single maps (Open the map, then go to Options, Set Map Size, then increase the Z value).
Now your probably wondering what happens when I compile MapA.dmp (With 2 Z levels) and MapB.dmp (With 3 Z levels).
Basically you just add MapB.dmp on top of MapA.dmp as if it were extra Z levels. (MapB.dmp Z level 1 becomes Z level 3)

Anyway, back to your question. Now you hopefully understand co-ordinates, so you can locate based on co-ordinates. locate(1, 1, 2) will send you to X=1, Y=1 on Z level 2 (Aka, Test2.dmp)