read this.

http://uscis.gov/graphics/fieldoffices/SCNational/index.htm#H

especially #13. You yourself can be the translator. just sign your name in the printed affidavit INS requires as below:

Please submit certified translations for all foreign language documents. The translator must certify that s/he is competent to translate and that the translation is accurate.

The certification format should include the certifier's name, signature, address, and date of certification. A suggested format is:

Certification by Translator

I (typed name), certify that I am fluent (conversant) in the English and (foreign) languages, and that the above/attached document is an accurate translation of the document attached entitled .

Signature
Date Typed Name Address