identify where the static variables are stored

They are stored in some statically defined block of memory statically reserved by the moment when the application is loaded and is ready for execution; it's size is statically known to runtime system. That is, this is not stack and not heap. The implementation depends on the implementation of JVM and host OS.

Technically speaking, in some system, stack and static memory share the same memory unit, from the OS point of view, but logically/functionally they are still isolated, so what I said in the paragraph above is still true. Again, implementations can be different, but functional properties of this memory are the same.

I don't think the word "identify" in your question title makes sense. Perhaps you need to understand that static fields belong to the class itself, not to each individual instance. The object of a field is only one per class. Sometimes, such fields are called "class fields", as opposed to "instance fields".

Now, if a field type is of reference type, it should be obvious that only the reference object itself is stored in the static memory block, but the referenced object is on heap. Here, you need to understand that any object of reference type is represented by two objects in memory: the reference part (analog to pointer in native memory systems) and referenced part.

—SA