The unit of the output from these sensors is? How can I convert it to LUX?

Well, it is only a simple analog sensor that could show you the relationship of the light intensity (within its detect range) and voltage (0-5V). If you want to transfer the voltage to unit in LUX, then well, it requires that you have a commercial Light Intensity Meter like this that can display LUX info, then you can match the readings to the sensor's analog reading, then you could a map to describe the relationship of voltage and ambient light density.