I am using a biblatex package and this error pop-ups "Style 'apa' not found"

This is my sample tex tagging and I am using a miktex v 2.8.

\documentclass[man,babel,american]{apa6}
\usepackage{csquotes}
\usepackage[style=apa,backend=biber]{biblatex}
\DeclareLanguageMapping{american}{american-apa}
\DeclareSourcemap{
    \maps[datatype=bibtex]{
        \map{
        \step[fieldset=doi,null]
        %\step[fieldset=url,null]
        \step[fieldset=isbn,null]
        \step[fieldset=abstract,null]
        \step[fieldset=month,null]
        \step[fieldset=eprint,null]
    }
}}


\addbibresource{test}
% @article{ref1,
% Author = {Jee N.},
% Journal = {Journal of Physical Sciences},
% Number = {1},
% Pages = {33 - 58},
% Title = {Sample Title.},
% Volume = {15},
% Year = {1994}}

% @url{ref2,
% Author = {Cabusog, E P.},
% Title = {Tetris {AI}},
% Url = {http://ift.tt/1ytcPnc},
% Year = {2012}}


\begin{document}

Sample paragraph~\cite{ref1,ref2}.

\end{document}

And here's the error and log.

(C:\MiKTeX2.8\localtexmf\tex\latex\biblatex\latex\biblatex.def)

! Package biblatex Error: Style 'apa' not found.

See the biblatex package documentation for explanation.
Type  H <return>  for immediate help.
...

l.10838 \RequireBibliographyStyle{\blx@bbxfile}

?