I currently have a seperate grid. The vertices inside the circle equals to the vertices on the outer edges on the grid and I would like to displace all the vertices so that they fit inside the circle. Can anyone explain to me how to achieve this?
You can use the 'Grid Fill' GN group from this answer to make the transition from grid to circle, or any other shape with the same vertex-count in the perimeter:
(Depending on what you need, you could expose the Mix factor to the interface of a regrouping of your own)..