Hi
as you have given no clue to your location and thus to which your regional settings are ( mm/dd/yy or dd/mm/yy),try it this way:
select the column containing the dates
Data tab - text to columns
Check "delimited"
Click Next twice
Select "Date"
Change the drop down box to MDY
Finish
If it does not work, try variations with the dropdown box.

( giving your approximate location in forum CP helps)

__________________
Did you know you can thank someone who helped you? Click on the tiny scale in the right upper hand corner of your helper's post