If you see here:
JsonConvert.DeserializeObject(T) Method (String)[
^] :
Expectation is to have a class where you have written 'className'. Though you have not given much info on it, but the naming and the error seems to suggest it's a variable name and not a Type.
In method:
JsonConvert.DeserializeObject<T> Method (String)
T => The type of the object to deserialize to.
Put a type, and it should work.