Forget sugars, it's all about carbs, they turn to glucose in your bloodstream.
So 28g of a 100g bowl of porridge is carbs.
So a 200g bowl would be 56g & so on.
Next step is to get a meter, eat that bowl of porridge (if you wish) & see what it does to your glucose levels, test every 30 mins to get a good idea.
The rules for prediabetics are the same as for full blown T2s, reduce the carbs in your diet to get you blood sugar back to normal.
Many studies on how weight loss & exercise can reverse prediabetes.
Consider yourselves lucky, it's estimated that a 3rd of Americans have prediabetes & 90% don't even know it.
Now you've a chance to act.