Hi,
(Make sure to check your email and spam folder to validate your forum account.)
How you move boxes will depend on the rest of your Unity project. For example, is it a first/third person game with a player character like Fortnite? Is it an avatar-less game like StarCraft or Civilization? Is it something else? Actually moving the boxes is almost certainly outside the scope of the Dialogue System, and you'll have to use something else to handle that part.
But to update the quest, you can probably use a
Dialogue System Trigger. For example, add a trigger collider to location B. Set the Dialogue System Trigger's Trigger dropdown to OnTriggerEnter, set the Conditions > Required Layer or Tag to the box's layer or tag, and configure the Actions section to increment your quest in one way or another. You'll also want to lock the boxes in place in location B or get rid of them so the player can't just pick up the same box and drop it in again. Note that this is just one way to do it. Sorry to be vague, but it's hard to provide specifics without knowing the rest of your project.