But if Jablka is the nominative singular, isn't the genitive plural the -ow? (Sorry for missing accents)
jabłko is nominative singular
jabłka is nominative plural
the verb is "ma", so it requires accusative.
Jabłko is neuter, so both singular and plural have nominative=accusative
-ów ending is for plural masculine nouns that end with consonant.
i wrote "farmer ma jabłka" and it says is an error. Correct that please