I recommend the official tutorials on this site.
Tutorial: Get started with Razor Pages in ASP.NET Core
If you do not see the "ASP.NET Core Web App" then you probably did not install the ASP.NET Web Development Workload.
Open the Visual Studio Installer. Click the "Modify" button and install ASP.NET Core Web App.
Or use the CLI command.
dotnet new webapp -o aspnetcoreapp