People are usually mixing up two things. [C# 3.0 & .NET Framework 3.5]

as people describe it previously and provide tables for each c# language version with its compatible visual studio and .net framework.. ::C# 3.0 was the version of the programming language released in 2007, and it came with awesome features like LINQ(to treat with data)

At the same time, there was an update called .NET Framework 3.5 which added tools for Developers.

the confusion because of the .NET Framework 3.5 was released around the same time (after c# 3.0 ) so Some people Mistakly think of it is an C# 3.5, but actually c#3.5 doesn't exist.

It’s just C# 3.0 with extra tools from .NET Framework 3.5.