To find position of item in container in ax 2012 you can get idea from below code. Confind method used to get position details of items for container.
container c ;
int i;
int j;
;
c=conPoke(c,1,"item1");
c=conPoke(c,2,"item2");
c=conPoke(c,3,"item3");
i = conFind(c, "item2");
j = conFind(c, "item3");
print "Position of 'item2' in container is " + int2Str(i);
print "Position of 'item4' in container is " + int2Str(j);
pause;