Seems a little odd, but the vi you are looking for is called "tktds3k Configure Acquisition Record.vi". The horizontal scale can be set with the "time per record" input. This is the total record time so it should be ten times the horizontal resolution. For example if you want 1 ms per division, set the time per record to 10ms as the scope displays 10 divisions. Tek's later scopes have much cleaner interfaces.
If you are not using LabVIEW you can use the HORizontal:MAIn:SCAle header. The argument for this does not need to be multiplied by 10.