You are right. The AudioBox only can record 2 tracks, cause this Audio Interface/Soundcard only can handle 2 inputs.
You need an Audio Interface/Soundcard, which can record or already has 8 or more channels.
You could buy an Audio Interface (https://www.presonus.com/products/Quantum-4848) and 8 Pre Amps (https://www.presonus.com/products/DigiMax-D8 or https://www.presonus.com/products/DigiMax-DP88). This would be a professional option.
You buy an Audio Interface, which already has 8 Pre Amps (https://www.presonus.com/produkte/de/Studio-1824 or https://www.presonus.com/produkte/de/Studio-192 or https://www.presonus.com/produkte/de/Studio-192-Mobile). Or a cheaper solution would be B ehringer UMC1820.
This would be much cheaper, and also really good sounding option.
Have in mind, that an Audio Interface is not a Pre Amp
I hope this helps you. If you have any questions, feel free to ask