It was introduced by the imigrants when they came into the country.
it was brought into the country by the immigrants
it was introduced = 紹介された
it was brought into = 持ち込まれた
immigrants = 移民
into the country = 入国
It was introduced by the imigrants when they came into the country.= 移民は入国した時に持ち込まれた。
it was brought into the country by the immigrants = 入国した移民によって持ち込まれた
なお、「ねぇ、知ってた?。。。」と言いたい時は
"hey did you know that ......?"
"I bet you didn't know that..." = 「◯◯って知らなかったでしょ」
1) 移民は immigrant(移民=イミグラント、と語呂合わせのようで覚えやすいです)と言いますので、シンプルに
They were brought by immigrants.
として頂ければ大丈夫です。They の所を変えて、
The food was brought by immigrants と言ったり、
The drink was brought by immigrants. と言ったりもできます。