Hi Jessica,

Convert your txt file in following fashion (mind the gaps, use Copy/Paste):
---------------------------------------------------------------------------
PKT-NR X Y Z CODE

1, 452139.568, 111499.729, 0.000, 0
2, 452134.098, 111499.261, 0.000, 0
3, 452133.953, 111500.955, 0.000, 0
---------------------------------------------------------------------------
After that save the file and convert extension from .txt to .re2

For import procedure check following help files (Works also for older Allplan versions):

http://help.allplan.com/Allplan/2016-1/1060/Allplan/index.htm#5949.htm
http://help.allplan.com/Allplan/2016-1/1060/Allplan/index.htm#8926.htm

For DTM check Terrain related help files.