Best is to check with your Country related Food regulations website, Food authority etc. However one may require experience with food services industry, or hospitals or food companies or SMEs (or any such related field), where you can perform internal audits after you gain ground knowledge. Further apply for external auditor course, and depending on the number of hours you get to audit (or depending on how it works in your country), you could become an external auditor.
On a general note, i felt auditor courses are only basics, but experience matters a lot, for example with a country based agency who do this regularly.
This is also probably an area that offer huge job scope for upcoming graduates, due to the current covid (reasons and food safety, hygiene matters become even more crucial). Hope that helps