Then you will need to see if you can purchase replacements from Apple. Yours is an obsolete model, so Apple may no longer have replacements.
Apple Store Customer Service at 1-800-676-2775 or visit online Help for more information.
To contact product and tech support: Contacting Apple for support and service - this includes
international calling numbers..
You can look for discs on eBay, ask the seller to provide them, and purchase a copy of Snow Leopard:
You can purchase Snow Leopard through the Apple Store:Mac OS X 10.6 Snow Leopard - Apple Store (U.S.). The price is $19.99 plus tax. You will be sent physical media by mail after placing your order.
After you install Snow Leopard you will have to download and install the Mac OS X 10.6.8 Update Combo v1.1 to update Snow Leopard to 10.6.8 and give you access to the App Store.