The index of an array begins with 0 (zero).
Thus, if you have 32 enemies and their id begins with 1 you should use:
epos[my.ENEMID-1][...]

Next thing: What is '_x' etc. supposed to be?
If you have an array epos[32][3]
You can get a single value with the following indices:
epos[i][k] where i is in { 0,1,2,...,31 } and k is in { 0,1,2 }

Or what exactly is your problem?