How can you find out how many races you have done in Mario kart wii?

If you're talking about Mario Kart Wii:

Go to your licence, and when the main menu screen comes up, click "Licence Options" and click "Records" and you will find out how many races you have raced. Note: The race count does not count towards Wi-Fi races. Those are counted in the Wi-Fi records bit.

The wins count is how many people you have come above, and losses is how many people you have come below in the final race standings.