1. your Full name (that is in your passport)

2. Your parents (both father & mother's name)

3. Your date of birth

4. Your place of birth.

The letter might contain one sentence like "It is certified that "Mr. ABC", son of "Mr. Your father" and "Mrs. your mother" was born in XYZ VDC- 2, Kaski Nepal on 22/2/2022 AD." 

The letter should bear the stamp of VDC (or Municipality), and signature of the secretary. If it is issued in Nepali language, it should be translated into english, - you can do that from kitabkhana.. but these days most of vdcs or municpality issue it in english. And you should submit the copy of nepali and english translation. 

You can not use anything else (passport, any other certificates etc.) as your birth certificates..USCIS does not accpet any other documents as your birth certificates.

I hope it helps. Best of luck.