I have Umbraco 7.6

I am trying to enable ModelsBuilder in API mode. As far as I learned in my version of umbraco Umbraco.ModelsBuilder.Api should have already been part of the Umbraco.Core and installed.

However when I check in my Developer > ModelsBuilders tab I can see this:

ModelsBuilder is enabled, with the following configuration:

The models factory is enabled.
The API is enabled but not installed.
External tools such as Visual Studio cannot use the API.
No models mode is specified: models will not be generated.
Models namespace is Umbraco.Web.PublishedContentModels.
Static mixin getters are enabled. The pattern for getters is "Get{0}".
Tracking of out-of-date models is not enabled.

In my web.config I have this:

  <add key="Umbraco.ModelsBuilder.Enable" value="true" />
<add key="Umbraco.ModelsBuilder.EnableApi" value="true" />
  <add key="Umbraco.ModelsBuilder.ModelsMode" value="Nothing" />

Since it says:

The API is enabled but not installed.

I tried to install Umbraco.ModelsBuilder.Api but have not found any information which ModelsBuilder versions are compatible with Umbraco 7.6 so I installed the latest 8.0.4 into my start Web project.

I installed VS extension and created a separate project to hold models eg. MyProject.Umbraco.Models, right-clicked Builder.cs file and clicked 'Run custom tool' (which I previously set up in the Builder.cs properties.

It does something but at the end it throws an error:

UmbracoModelsBuilder: Starting v8.0.4 10/05/2019 18:29:01.
UmbracoModelsBuilder: UmbracoModelsBuilder failed to generate code: UnsupportedMediaTypeException: No MediaTypeFormatter is available to read an object of type 'IDictionary`2' from content with media type 'text/html'.
UmbracoModelsBuilder:    at System.Net.Http.HttpContentExtensions.ReadAsAsync[T](HttpContent content, Type type, IEnumerable`1 formatters, IFormatterLogger formatterLogger, CancellationToken cancellationToken)
   at Umbraco.ModelsBuilder.Api.ApiClient.GetModels(Dictionary`2 ourFiles, String modelsNamespace)
   at Umbraco.ModelsBuilder.CustomTool.CustomTool.UmbracoModelsBuilder.GenerateRaw(String wszInputFilePath, String wszDefaultNamespace, IntPtr[] rgbOutputFileContents, UInt32& pcbOutput, String& errMsg)

Anyone can help with this?