我曾经去过杭州用英语可以说 "I have been to Hangzhou."
"I have been" 是一个完成时的短语，它表示过去发生了一个动作，并且这个动作对现在产生了影响。 "to" 是介词，表示“去”， "Hangzhou" 是地点名称。
例句:
I have been to Hangzhou before. (我以前曾经去过杭州)
I have been to Hangzhou, it's a beautiful city. (我曾经去过杭州，那是一个美丽的城市)
I have been to Hangzhou last summer. (我去年夏天去过杭州)