The whole idea of chunks in all frameworks I've encountered so far, incl. Minecraft is to have them in a spatial grid. Especially so that calculations like these become trivial.

The framework you use most likely provides you some coordinates for every chunk in the world. Either in real world X & Y of the chunks corner, or as Chunk X and Y which you have to multiply with the size of a chunk. Minecraft shows all that in the debug screen.

With those numbers using colliders is absolute overkill. It's just good ol' pythagoras to get distance to the player.

Do you actually use a chunk based voxel framework that does not have that? Does it use chunks of different sizes somehow?