what bus number i should take from hk central to yuen long?and how much the fare in the bus?

Walk from where you are to HSBC Main Building, Des Voeux Road Central to take bus no. 968 or 968X to get off at YOHO TOWN.Then you can walk to your destination at Yuen Long. The whole journey takes 55-60min and the bus fare is 22.7HKD.

You can also take the MTR for this journey. Walk from Central to HK Station to take Tung Chung line to Nam Cheong, where transfer to West Rail line to Yuen Long. It takes 40min and MTR fare is 24.6HKD.