Currently Being ModeratedNov 1, 2013 5:31 AM (in response to Andrei Tchijov)
Snow Leopard and Snow Leopard Server both predate the App Store and related software downloads.
Snow Leopard Server (OS X Server 10.6) was generally available only via DVD distribution, and there were only specific versions produced; you'd need a version that supports your particular system, or to use the streaming update to get from client Snow Leopard to Snow Leopard Server (if your system requires a later version and can't boot the server DVD directly).
Your options here are to roll in your backups, or to roll in Snow Leopard Server from either your server-specific DVD distro or from a retail Snow Leopard Server DVD distribution.
If you no longer have your distribution, you might find a Snow Leopard Server distro from the used market — you'll need a license key to activate it, and you'll want the retail distribution and not the server-specific version — or maybe directly from Apple Support folks. If you were licensed for Snow Leopard Server and had purchased directly from Apple, then you might be able to call Apple Support and get access to what you had, too.
It used to be that the per-system DVD disks around that era were grey, and the so-called retail disks — which is what you want, if you don't have your own grey disks for your system — were black. I don't have any retail Snow Leopard Server DVDs handy to confirm that coloration, though.