300 is a small amount, just bring cash directly, and you don't need an ID card.
You can also go to several banks and ask what the exchange rate is. At present, the quotation of China Bank is around 6.3, but the actual exchange rate is generally lower. That is to say, your 300 is about 1800- 1890. Sometimes the exchange rates of different banks are different. Compare yourself and see which side has changed more.
Believe me, I specialize in foreign exchange. If you find it useful, adopt it. Thank you.