I had fifteen pieces of sushi and two rolls of Kanpyo-maki.
ーI had fifteen pieces of sushi and two rolls of Kanpyo-maki, which are strips of gourd wrapped in rice and seaweed.
「私は寿司を15個と、細長く剥いだ瓜を米と海苔に巻いた干瓢巻きを2本食べた」
寿司の数え方は、握り寿司なら a piece of .../ pieces of ... のように言います。
巻き寿司なら、a roll of .../ rolls of ... のように言えます。
ご参考まで！
カナダ 
