He will be able to tell you how many you need and what you need for edge restraint depending on the type of soil.
He will also have the installation instructions and the pattern options. If he does not have this simple information, avoid him and go to a real paver supplier.
In general, you will need 4-6" of compacted base and a 1" sand setting bed. After laying, sprinkle masons sand and vibrate the surface with a plate vibrator. You supplier can also steer you to the right base and sand, using your local terminoplogy.
You can also look at the Interlocking Concrete Paver Institute (ICPI) site for instructions and technical advice.