Microsoft Remote Desktop, but the only version in the app store is not supported with my os.

I’m sorry, but your macbook’s latest macOS it can update to is OS X El Capitan.

try going to Microsoft remote desktop’s website and see if there are any previous versions up for downloads that are compatible with OS X El Capitan.

You could try the Microsoft site. Before they put Microsoft Remote Desktop Connection client in the App Store, you could download it directly from Microsoft.

You could try CoRD

http://cord.sourceforge.net/