[Solved]List.FindIndex error C#

Hi, I am trying to perfom this code but it keeps throwing me this error. I looked it up and didnt find nothing useful.

public int getBlockIndex(Vector3 pos){
int index = ChunkBlocks.FindIndex(pos);
return index;

}

Error:

Assets/Chunk.cs(44,49): error CS1502: The best overloaded method match for `System.Collections.Generic.List<UnityEngine.Vector3>.FindIndex(System.Predicate<UnityEngine.Vector3>)' has some invalid arguments

And

Assets/Chunk.cs(44,49): error CS1503: Argument `#1' cannot convert `UnityEngine.Vector3' expression to type `System.Predicate<UnityEngine.Vector3>'

Any ideas, Suggestions fixies or explanation why this is not working?
As far as i know is something related to delgates which i dont know what they are, I tried to fix it but i couldnt.

Thanks.

FindIndex takes a predicate like this:

     int index = ChunkBlocks.FindIndex(d=>d == pos);

I think you really want IndexOf right?