Until lately, if you were looking to convert from asin to ean,upc and other codes (or from ean and upc to asin) you had to pay for it (specially if you wanted bulk conversion).
Now there is a new site that converst asin to ean, upc and more for free (also bulk conversion). no money needed,no registration. the site is http://www.asinlab.com/. Try it,I'm sure you will find it useful.