how to measure the transform ability of a query on Internet Advertising

hi all, I have a task which aims to measure the transform ablity of a keyword , the transform ablity can be understood as the probability of a query on the search engine brings an order to the customers.For example, I searched "apple" on the search engine then I go the website and buy a notebook, then "apple" bring a transaction to the apple company and the query "apple" has a strong ability to bring a transaction. (Maybe this example is not good but it could explain the idea)

Now I have the query log and the click log of advertisement on the search engine , how can I use these data to analyze the transform ablity of a query ? I think maybe some clarification algorithm could give answer but I'm not sure the result though.

Could you please give me some hints? Any feedback will be appreciated!