Suggest me Arduino device with USB for Mass storage I want to make a temperature data logger by using Arduino.

I can read a data every 1sec and I want to store 30days data with date&amp;Time.

In data logger, I want to write a temperature data with date&amp;time in the .csv file and this file will be generated after I attaching USB.

So, Please suggest me Arduino board with USB compatible(working on 3V battery) and also suggest me EEPROM who able to store 30 days data.
60 samples per minute, 60 minutes per hour, 24 hours per day, 30 days - that's 2592000 samples. At 10 bytes per sample (a very generous allocation) that's less than 30MB of data.

You could fit that many many times over on even the smallest of today's SD cards, so why mess with the complexity of USB? Any Arduino can work with an SD card.

A bigger concern of yours should not be the storage medium, which is trivial - you should instead be thinking about how you will run the board off a 3V battery for 30 days.