How do I know which keyword resulted in a conversion

If you have activated conversion tracking to your tracking links and have included the appropriate syntax to your destination URL's (see below for appropriate links) you will be able to view which keywords are converting. 

From the dashboard you will click the black "REPORTS" button and select "conversions"

At the conversion tracking view click the hyperlinked number to the right of the conversion name to view the event by event list of conversions. 

Depending on the platform and the reporting, the keyword will appear either in the "Keyword" or "Query Parameter" column in reporting. To show this data you will need to click the grey wheel icon on the top right of the reporting view.