You can install this specific version from NuGet.org or GitHub Packages using either of these commands:
Using the Package Manager Console:
PM> Install-Package MikaelDui.HtmlAgilityPack.Extensions --Version 0.0.3
Using the .NET CLI:
dotnet add package MikaelDui.HtmlAgilityPack.Extensions --version 0.0.3
But it's preferable to use floating versions, see the Microsoft Docs.