what is the time of the ferry from hong kong airport to zhuhai on 10th of October around 5pm.

At 17:00 (a later ferry and the last one is at 20:00), a ferry leaves from Skypier near HKIA to Zhuhai. After landing, no need to go through the immigration. Just walk to Arrival Level, T1 and buy the ferry ticket on the spot (no need to book in advance unless it is peak travel season) at the Ferry Ticket Counter at Transit Area E2. There you need to show your luggage tag receipt and they will help you handle the luggage. Afterwards, go to the ferry boarding entrance to scan your ticket and check the status of your luggage. Then hop on the ferry to ur destination.

If you will leave HK by air on 12th, it is fine to use the back ferry. The earliest one leaves Zhuhai Jiuzhou at 09:30.