133015 extract files from hard drive

i am notorius for saving duplicate files of various types (ie. word, pdf, etc) in various folders on my hard drive. I would like to extract files of a particular type and have them saved in a folder on my external hard drive, so that i may sift through and organize. The only problem is there are many duplicate files and I only want to grab one instance of each file but i need to make sure that duplicates are chosen byte for byte and not just by name because many files bear the same name but have different data. I need this asap for a project i am working on