There is no direct flight from Pakistan to Jiujiang. If you depart from Islamabad, there are connecting flights with one or two transfers to Jiujiang. For one transfer, u could take flight to Beijing first and then to Jiujiang by another flight. And the direct flight from Islamabad to Beijing is only available on each Thursday and Sunday. For more details, you can search on the website or consult some travel agencies in your own country after your traveling date is fixed.