How do you think Mr. Fox knew the way so well?

Mr. Fox knows the way because he's been to the farm before..... he's been there often.

Mr Fox grinned again, showing even more white teeth. ‘Look,’ he said, ‘I know my way around these farms blindfold. For me it’s just as easy below ground as it is above it.’ He reached high and pushed up one wooden floorboard, then another. He poked his head through the gap.