Note: not a teacher.
I am a wise experienced shopper. I know all the prices of foods(pluralized?) at the supermarkets
- As you have written the sentence, it should just say food.
- If you mention varieties, as in the second sentence, then you may say different foods like cookies etc.
Is the word food correct but there are things like cookies(snacks), meat, juices(not food/foods)
All the items you mention, snacks, cookies, juice, meats are various foods. (or items of food)