1. Clich on Start Menu, Control Panel, Administrative Tools, Internet Information Services (IIS) Manager.
2. Click on Application Pools, and locate the application pool for your web site.
3. Right click on the application pool and click on Basic Settings.
4. Change the ASP.NET version from the drop down menu under .NET Framework Version.

C# 8.0 and .NET Core 3.0 – Modern Cross-Platform Development: Build applications with C#, .NET Core, Entity Framework Core, ASP.NET Core, and ML.NET using Visual Studio Code, 4th Edition
ASP.NET Core 3 and Angular 9: Full stack web development with .NET Core 3.1 and Angular 9, 3rd Edition
C# in Depth, 4th Edition