Up we go, up we go, which place does up refer to? How did the mole manage to move up?

The place is the meadow...... in order to get there he "scratched and pulled" his way up.

So he scraped and scratched and scrabbled and scrooged and then he scrooged again and scrabbled and scratched and scraped, working busily with his little paws and muttering to himself, ‘Up we go! Up we go!’ till at last, pop! his snout came out into the sunlight, and he found himself rolling in the warm grass of a great meadow.