How do I turn on the scanner option in notes

This support article tells you how to scan into Notes.

You can also tap the 3 dots in the upper right and tap Scan.

How to scan documents on your iPhone, iPad, or iPod touch - Apple Support

I believe you also need to be using an iCloud Note. ie, you cannot do this in a gmail synced Note

If your details are correct and you are using iOS 13, you should update to iOS 14.