Postmates get paid weekly via direct deposit for all deliveries completed between Monday–Sunday of the previous week (the week ends Sunday at midnight PST, and deliveries completed after 12:00AM on Monday will be processed the following week). Payments are transferred directly to your bank account and usually take 2–3 days to appear, so earnings that you did not withdraw instantly should show up in your bank account by Wednesday or Thursday.
If you don't want to wait for your direct deposit, you can always withdraw your earnings beforehand by using instant deposit.
Please see the Delivery Earnings section in your Postmates dashboard to track individual deposits. Clicking on a specific deposit will show a breakdown of the amount.