On the back of most pre-packaged things these days, whether it's a loaf, a bag of flour or pasta, a tin of peas or whole meals, and everything in between except fresh fruit and veg - oh and supermarket own bakery bread - there is nutritional info, in little writing.
You are looking for 'carbohydrates'. That will say 'of which sugars' underneath, but for the purposes of this conversation, you can ignore that part. Sugar is just another carbohydrate, and weight for weight, is near enough ALL carb and nowt else to speak of really.
If you are comparing two brands of something and they are virtually the same carb value, THEN consider the 'of which sugars' and take the lower.
I should add, if per 100g weight, the product has a large proportion of carb and of that sugars make up a large proportion, best not touch it with a bargepole at first.
eg I have a pack of hot cross buns here. Per 100g weight, carbs are 49.9g - so HALF of every morsel is carbs. Far too much! Of that 49.9g, 18.4g is sugars. So about a fifth of every morsel, is SUGAR. Far too much again!
Protein and fats (meat, fish, cheese, eggs, butter etc) have either none or virtually zilcho carbs.
Root veg have more carbs than green leafy, legumes (peas and beans) have a bit but shouldn't concern you unless you eat shedloads. Baked beans would be fine, were it not for the tomato sauce, which is fairly evil from our point of view!
Berries generally have less carbs than any other fruit - bananas are a bit of a step too far for a lot of us. A Satsuma type orange may be OK, but a Jaffa should be considered more or less the same as bananas. Approach with caution.
Once you get on an even keel, it may be possible to put some carbs back in, in small enough quantities you should get away with it - but the ONLY way to find that out is with your meter - 'Test, Review, Adjust'.