I wanted to know how to get the notional value of the corporate bond using the sfc api
The question likely to be data/content question.
However I did a quick check with data support and found that the Notional value seems to be the Issue Amount from the bond overview. That gives the original notional amount at the time of issuance. For Real-Time data some RIC/Exchange use FID 1054 to represent the data. Not sure is this the data you are looking? If not what RIC / Exchange you are using?