Extension Cord help

[wowzer]

I want to pull a 30amp 240volt cable from my generator located outside to inside my garage to power my 4 prong outlet and my home circuit breaker. What gauge cable should I use? The distance is roughly 40 feet. Out of curiosity, what if I needed a 60ft cable?

The generator is 8000watts/10,000 peak watts from Generac XP8000E

Thanks.