How can I export 3d model from unity3d file?

there is not any built in feature for what you want. you can access mesh data and write them to the format that you love. for textures it's easier because there is a function for encoding the data to PNG format. the EncodeToPng gives you an array that you should write to a file yourself. there is a script inside the unify community wiki that exports models to obj format. the script is not much complete and don't export animations or skins&bones and ... the script is called ObjExporter. there is another one called TerrainObjExporter for exporting your terrain.