I am sorry there is no USCIS field office in Nepal. The nearest one from Nepal will be in New Delhi.
India - USCIS New Delhi Field Office
https://www.uscis.gov/about-us/find-uscis-office/international-offices/india-uscis-new-delhi-field-office


https://my.uscis.gov/en/appointment/new?appointment%5Binternational%5D=true