I accidentally deleted garageband and I can not find the disks how to recover it?

Do you have a backup you can restore from?

Replacement System Discs can be obtained from Apple's Customer Support - US (800) 767-2775 for a nominal fee. You'll need to have the model and serial number of your Mac available.

If you're not in the US, you may need to go through the regional Apple Store that serves your location to find the contact number - http://store.apple.com/Catalog/US/Images/intlstoreroutingpage.html

The relevant Apple Online Store phone number is given at bottom left of this page (assuming your country is correctly shown at bottom right).