I have WD3200BEVT laptop HDD. Which is best External Hdd case for It. I want to make it external HDD?

This is a standard SATA laptop drive so any modern caddy will do.
http://www.cclonline.com/category/703/Storage/External-HDD-Enclosure/

This is a WD Scorpio Blue drive. It's a SATA II drive. You can use any USB to SATA enclosure. It would be better to look for a USB 3.0 as this is the fastest USB standard currently available.