regarding appointment of new auditor due to resignation.

Is you new Auditor Asking for NOC

better is get a resignation letter from old auditor, But the new auditor need to follow the CA Bye-laws and need to get NOC from old auditor too

You can get all documents regarding the appointment of new auditor due to the resignation of old auditor at https://corporatedrafting.com/product-category/document/compnies/auditor-appointment/appointment-of-auditor/