Your value contain three spaces. So if you split at space then index 1 will give you mm/dd/yyyy and index 2 will give you hh/mm/ss and index 3 will give am/ pm.
Now you can choose which index you want
Select list item list split at spaces (list name) index (1) will give you the mmddyyyy
But instead of using such things why don’t you use format date block?? It will be very convenient