。
Many farmers in Hokkaido grow potatoes.
Literal
Hokkaido [of-の] many [of-の] farmers [topic-は] potato [object-を] grow-am.
多くの農家 ('many farmers') uses the attributive 多くの. 農家 literally '[farming] house, farming family' = 'farmer, farming household.' じゃがいも is written in hiragana (katakana ジャガイモ also common); from the Javanese/Portuguese 'Jacarta potato' — a 16th-century Portuguese-introduced food. 栽培する ('to cultivate, grow').