Hi. I gained my US citizenship through one of my parents. I was born overseas and my primary proofs of US citizenship are my passport and Report of Birth Abroad (FS-240) both issued by the State Department. I'm looking ahead at I-134 and line 1b would be the most appropriate line for me to fill in but the document they are asking for is a citizenship certificate number which issued by the USCIS . Would I need this specific document? It costs $255 so I would rather not spend on it if my current documents will be enough. Has anyone experienced this issue ad know more info?

Thanks!