小籠包英文係什麽

Since there is no such particular thing in western culture, " dumpling " is just a general term of almost any kind of 餃子. " Pork dumplings " or " pork dumplings in soup " could be 水餃 too. I think you may say " steamed pork dumplings in Shanghaiese style " to describe 小籠包.
PS.: I won't recommend to use " bun ", since bun is kind of bread, which 小籠包 is not a kind of bread.

小籠包英文是 Steamed pork dumpling. 台灣有名的鼎泰豐小籠包就用這個英文名。

小籠包英文係Steamed Pork Dumplings