There is direct train from Urumqi to Xiamen, you need to transfer at Beijing or Xian. BTW, train trip from Urumqi to Xian costs around 30 hours and train trip from Xian to Xiamen takes around 35 hours, if possible, better take flight which take around 7 hours. From Xiamen to Chongqing, you can take the only train at 18:24. The train takes around 12 hours to reach Chongqing and it costs CNY242-671.