Celebrate the Harvest looks at the creatures you control as it resolves to determine how many basic lands cards you can search for. For example, if you control a 1/1 creature and a 2/1 creature at that time, there are two different powers among creatures you control.
Search your library for up to X basic land cards, where X is the number of different powers among creatures you control. Put those cards onto the battlefield tapped, then shuffle.
