Mohe usually takes 2 or 3 days to play. If you plan to go to Mohe, even if you fly back and forth, you can only go to Harbin for another day, which is not enough time. It usually takes one or two days to play in Harbin. If time is tight, you can also play for one day and go to the world of ice and snow for one night. If you are in a snowy country, it will take you five or six hours from Harbin to stay for one night. The next morning, you can watch the sunrise on Yangcao Mountain and climb a mountain. In the afternoon, you can go to rime island or Changbai Mountain. Rime island can stay for one night. If you go to Changbai Mountain, you have to spend at least one day and stay for two nights. You two only have four days. The recommended itinerary is Harbin-Xuexiang-rime island or Changbai Mountain. If you go to rime island, you can stay for one more night. If you go to Changbai Mountain, you can only stay for one night in Harbin. Besides, you said you wanted to go to Yanji, which is very close to Changbai Mountain. If you want to go, you can take a bus or carpool, and then take the high-speed train from Yanji to Shenyang directly. Generally speaking, you can choose carpooling or tourist bus from Harbin to Xuexiang, and carpooling from Xuexiang to rime island or Changbai Mountain. You can look for carpooling on Taobao.