Sony Alpha 7RIII RAW

Look here.

RAW data application software "Image Data Converter" Support| Interchangeable Lens Digital Camera "α" | Sony

This camera is not supported by Adobe software at this time. Most likely in a future update it will be supported. No one knows when this will be (except Adobe, and they never tell in advance).

I paid so much for a superb camera and I'm not able to use it.

In the meantime, YES you can use this camera. Use the SONY software to convert your RAWs to TIF, and import the TIF into Lightroom. Or shoot JPG.

Ask Sony why they failed to offer an option to save photos in DNG format. Using this publicly-documented format would have allowed LR to support the camera from day 1.

For now, there may be a LR update in the next month or so.