There are differences between languages here:
Yes, the plural form in English is "fruits", but that is only used when you want to stress they're different "types of fruit".
In Portuguese, though, you do "one, two, three frutas". Each "fruta" is a unit, just like "one, two, three oranges".
PS: of course you can still use the singular version in Portuguese sometimes when referring to a general thing, such as in "ele gosta de banana(s)", "ele gosta de fruta(s)".