C:\Program Files\Microsoft SQL Server\100\SDK\Assemblies is the correct folder location (or C:\Program Files (x86)\Microsoft SQL Server\100\SDK\Assemblies on 64-bit systems).
You need to add references to:
-
Microsoft.SqlServer.ConnectionInfo.dll
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Microsoft.SqlServer.Smo.dll
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Microsoft.SqlServer.Management.Sdk.Sfc.dll
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Microsoft.SqlServer.SqlEnum.dll
(These are the minimum files that are required to build an SMO application)
For SQL Server 2016, this location is C:\Program Files (x86)\Microsoft SQL Server\130\SDK\Assemblies (for the 64bit version).
Ref.: How to: Create a Visual C# SMO Project in Visual Studio .NET
The SQL Server Management Objects (SMO) are downloadable as part of the relevant SQL Server (20XX) Feature Pack (check the smallprint as I don’t believe these are redistributable?)