You will have to get your birth certificate (stamped letter) from your VDC or Ward. You will get a letter with both Nepali and English translation on the same page these days. As this is not your original birth certificate, you will have to ask your parents/siblings to write notarized affidavit of birth letters. All of these documents are required when you are filing I-485, so it is better to start collecting them after 4-5 months of PERM filing.