How to make it move a distance equal to its diameter which cannot pass through objects?

Question

Unity

Good afternoon! My name is Alice, I'm making a game in which a chip moves a distance equal to its diameter. Watch the video . I'm trying to do the same control, when "preview next move" cannot go inside another chip, then "preview next move" makes a decision to change the location to the nearest one where there is free space.
the main question is how to make it move a distance equal to its diameter which cannot pass through objects like in the video? can you help