mezuzah

Question

WELCOME BACK! 1) i measured a walk in closet that is an inch or two less than 6 feet wide and just less than 6 feet deep im not sure of the exchange of Daled amot by Daled amot which is what i thought is the criteria needed to place the mezuzah on the right post entering the closet - please advise 2) the closet has a folding door which covers the whole front of the door post - should i stick the mezuzah on the inside of the closet ON THE DOOR POST although its not visibla with the door closed