Unity3D 模型导入Error

在导入3d max模型的时候报错：

3ds Max could not be found.
Make sure that 3ds Max is installed and the max file has 3ds Max as its 'Open with' application!

造成的原因是因为我直接导入.max文件但是我电脑上面没有安装3Dmax.   unity需要导入.fbx才行。