Templates are a feature of the C++ language, so you don't have to to anything to set them up... debugging the error messages can be confusing though
I don't know much/anything about Autodesk's SDK, but have you made sure that you are linking your project to their static library (.lib) files?
L. Spiro is spot on with the interface changes... to get the count for a particular object type you should use :
FbxScene::GetMemberCount( const FbxCriteria &pCriteria ) const
So you fill in an FbxCriteria instance with the type of object that you're looking for... in your case FbxAnimStack:
FbxCritera searchCriteria = FbxCriteria::ObjectType( FbxAnimStack::FbxClassId )
Here's a link to the documentation, the GetMemberCount is part of the FbxCollection class, which FbxScene is derived from :
Hope that helps!