Karachi to danyang city and danyang city to guangzhou

There is no direct flights or cruise to reach Danyang, so in my opinion, you need to fly to HK first and then to GZ.
From there you can fly to reach Nanjing where you can find direct airport shuttle bus for Danyang.
The bus is not suggested, since the journey time is long and not safe. The only one train 1312 will take you one day to reach. So the flight is suggested.