Migration from old(Nuget.Core) to new client sdk(NuGet.Packaging & NuGet.Protocol)

In our old application we are using the following interfaces from NuGet.Core library.

IPackageIPackageLookupIPackageRepositoryIPackageAssemblyReferenceIPackagePathResolver

In the new 'NuGet.Packaging' library we could only identify the 'IPackageMetadata& PackageBuilder' classes. We need the migrating information about the above mentioned interfaces in the new client SDK (NuGet.Packaging & NuGet.Protocol).

FYI: We tried using IPackageMetadata, thought which is equivalent to old IPackage interface. In our old application, we used the following two methods in many places which belongs to IPackage.

IEnumerable<IPackageFile> GetFiles();Stream GetStream();

Also struggling to find the migration options for these two methods.

It will be helpful, if someone provide the guide information (any URL or sample) about all the class/interface and methods of the new nuget SDK.

Please help us here for migrating to new client SDK.