Problem:

Columns A:F contain values representing month, day, year, hours, minutes and seconds.
We want to combine the numbers from each row into a single date and time value.

Solution:

Use the DATE and TIME functions as shown in the following formula:
=DATE(C2,A2,B2)+TIME(D2,E2,F2)
Format the results (column G) as \"mm/dd/yy hh:mm:ss\".