can you please kindly advise on bus number can i take from guangzhou airport for zhongshan 8 road?

There is no direct bus there.
So you are suggested to take metro line 3 and transfer to line 2 at Jiahewanggang, then transfer to line 5 at GZ Railway Station, after that, get off at Zhongshanba from Exit D, then walk south for about 150 yards, you will get there.