You already posted the same question one week ago, and you got the same answer as given by Ben above. So, I suppose that your question was not fully understood. Could you be more explicit ? For instance, where did you get the date-time string from ? What further processing do you want to do with the results ?
The %j will give you the day of the year. Your problem is to convert your string into a time/date format. The attached vi shows how. Basically you need to split your string using Scan From String into the different fields (MM/DD/YY/hh/mm/ss), then bundle these into the time/date cluster, then wiring the cluster into the Date/Time to Seconds function. The output of Date/Time to Seconds is then wired into the Format Date/Time String function. You can create the time/date cluster by right clicking on the input terminal of Date/Time to Seconds and selecting Create Control.