I just installed Xamarin for 1st time and I have this error ?

MSB4062 The "Xamarin.Forms.Build.Tasks.GetTasksAbi" task could not be loaded from the assembly C:\Users\Asus\.nuget\packages\xamarin.forms\3.0.0.482510\build\netstandard2.0\Xamarin.Forms.Build.Tasks.dll. Could not load file or assembly 'netstandard, Version=2.0.0.0, Culture=neutral, PublicKeyToken=cc7b13ffcd2ddd51' or one of its dependencies. The system cannot find the file specified. Confirm that the <UsingTask> declaration is correct, that the assembly and all its dependencies are available, and that the task contains a public class that implements Microsoft.Build.Framework.ITask.   App2    C:\Users\Asus\.nuget\packages\xamarin.forms\3.0.0.482510\build\netstandard2.0\Xamarin.Forms.targets 36