This for future:- hi Jeeva if you install again unity with vscode please read this
First install vscode extension https://marketplace.visualstudio.com/items?itemName=ms-dotnettools.csharp
If you got error like this "The .NET Core SDK cannot be located. .NET Core debugging will not be enabled. Make sure the .NET Core SDK is installed and is on the path" then install https://dotnet.microsoft.com/en-us/download/dotnet/thank-you/sdk-6.0.300-windows-x64-installer
If vscode shows "The reference assemblies for .NETFramework,Version=v4.7.1 were not found" on output terminal then install developer pack https://dotnet.microsoft.com/en-us/download/dotnet-framework/net471 then try exit and open vs code if not work then restart

This for future:- hi Jeeva if you install again unity with vscode please read this
First install vscode extension https://marketplace.visualstudio.com/items?itemName=ms-dotnettools.csharp
If you got error like this "The .NET Core SDK cannot be located. .NET Core debugging will not be enabled. Make sure the .NET Core SDK is installed and is on the path" then install https://dotnet.microsoft.com/en-us/download/dotnet/thank-you/sdk-6.0.300-windows-x64-installer
If vscode shows "The reference assemblies for .NETFramework,Version=v4.7.1 were not found" on output terminal then install developer pack https://dotnet.microsoft.com/en-us/download/dotnet-framework/net471 then try exit and open vs code if not work then restart