Exchange player position to only 3 possible places with a platform

Hi. I am trying to make a sort-of platformer game where there are three platforms where the player can go. The player is walking and can go onto any of the next platform if he is at the edge of one. The user can drag and drop the platforms to exchange the platforms and the player will still be on the SAME(he will change position with the platform he was on) platform. See the image and read the image description to understand what I am saying(Sorry for the bad art, did this in 5 minutes).

Link: Click Here

Any help would be appreciated as I have some basic experience with Unity but I’m just 14 so this just goes a bit out of my league.

Hello, uptil now I was able to figure out this:

I am now wondering how to do the drag and drop as I have made it set to its default position by creating a variable which stores the position in the Start function. Now how am i supposed to make the user drag and drop the boxes only to those three places, I tried drag and drop videos and other forums but all the other were for UI elements, these boxes are sprites. Any help would reaaallly be appreciated