How to store difference between start time and end time in HH:MM:SS format.

I am trying to store difference between startTime & endTime  attribute in diffBetTime attribute (HH:MM:SS). what should be the data type of diffbetTime and how to calculate expected result in appropriate format? check below image for reference..  as i have done it In microflow using minutesBetween but i want eaxact HH:MM:SS format