The code of the PA office to which the FatturaPA file must be sent can be found at the Directory of Public Administrations website. Details on where and how to find the code required can be found in the documentation on the site itself (Guida IndicePA Area Pubblica [PAIndex Public-Area Guide - currently unavailable in English]).
F.A.Q. Public Administrations
Where can I find the office code of the administration to which my FatturaPA file is addressed, to be entered in the 'CodiceDestinatario' [Addressee Code] field of the DatiTrasmissione block?
What does a Public Administration have to include in the URI string at the site www.indicepa.gov.it during listing on the directory of Public Administrations?
Since the URI field must be filled in only if the channel through which the FatturaPA file is reached is different from the Certified Email, the value which must be entered is that indicated in the email that the Exchange System sends at the end of the registration procedure
