All model names use the following format: Helsinki-NLP/opus-mt-{src}-{tgt}
The language codes used to name models are inconsistent. Two digit codes can usually be found here, three digit codes require googling "language
  code {code}".
Codes formatted like es_AR are usually code_{region}. That one is Spanish from Argentina.
The models were converted in two stages. The first 1000 models use ISO-639-2 codes to identify languages, the second
  group use a combination of ISO-639-5 codes and ISO-639-2 codes.