we will go to ngong ping on morning and planning to go to victoria peak after lunch in HK. but how?

I think the local MTR can easily help you to do that.
From the Ngong Ping, you need to go back to the Tung Chung first. From Tung Chung Station, you can take the Tung Chung Line to get to Hong Kong Station. The you can change to the Island Land Line to get to Central Station. Get out of the station from Exit J2 and then you can walk along the Garden Road to reach the Peak Tram Station easily.