A problem… in the new model…

I am needing shape a imonológico system with some bacteria, and other composites, but necessary of one mesh of bigger size that “300 X 300”, and of preference in the 300 model 3D that “300 X 300 X 300” would be? I made some tests with models contained in the Models Library, but without success it returns me an error, and finds that he does not obtain to mount, somebody has some idea…