You don't have much hair on your legs. That's nice.
I wish I didn't have much hair on my legs like you.
I wish the hair on my legs was thin like yours.
ーYou don't have much hair on your legs. That's nice.
「足にあまり毛がなくていいね」
don't have much hair on ... で「…にあまり毛がない」
ーI wish I didn't have much hair on my legs like you.
「私もあなたみたいに足の毛が少なかったらよかったのに」
I wish ... を使って「〜だったらいいのに・よかったのに」
ーI wish the hair on my legs was thin like yours.
「私の足の毛があなたのみたいに薄かったらいいのに」
hair on one's legs で「足の毛」
thin は「（毛が）薄い」という意味もあります。
ご参考まで！
カナダ 
