Minecraft uses voxels. While they look like regular primitive cubes they are much different. Doing the same thing in Unity is no easy task. There are some voxel engines on the Unity Store but I don't know if they have Playmaker support, or if that would even make sense to have.
You could do something similar on a much smaller scale using Playmaker, but I don't think you would get the result that you are looking for. If this is your first attempt at making a game I would suggest doing something way simpler until you understand what you're undertaking with making something like Minecraft.
