Assembly files error

Hi folks.

So i have an issue with (i think) assembly definition files. I created this file structure:
- MyPackageFolder
- Animations
- Prefabs
- Editor
- Scripts
- EditorAssemblyFile
- Scripts
- ThirdPartyScripts ( this is where all plugins go)
- Plugin A
- Plugin B
- MyPackage AssemblyFile

The problem is: When i import the package to another project, i get an error of missing reference to one of the third party plugins. If i create an assembly file inside the ThirdPartyScripts folder, all my scripts looses references.

So, how can i fix this?

Best regards

 

If anyone gets this error.

Modify your package according to these https://docs.unity3d.com/Manual/CustomPackages.html.

I created the package before this documentation existed.
If need help, feel free to reach me.