As a rule, 2 to 3 days is enough for Katra tour package : 
Day 1: Arrival and settling in
Day 2: Vaishno Devi (entire trek or through helicopter)
Day 3: Local sightseeing (not obligatory) / departure.
You can also take a 4-day package with Kashmir Holiday Packages that will give you the opportunity to relax or include additional items in case you would like to go more slowly or use different directions.