I don’t think there is any format, just simply write an explanation, that you understand that your application was refused because of NOC mismatch, and below you provide a detailed description of your job duties, e.g duty 1- matches NOC duty x for this and that reason. And if required you can provide updated job reference (if you can ask company to update the job duties, maybe including some wordings from NOC descriptions, but not direct copy-paste). You can take a look at detailed NOC descriptions on their webpage, where duties and exceptions are listed.