Train To Impossible Places (2 Book Series)
From Book 1:

A middle-grade fantasy and nonstop adventure, The Train to Impossible Places by debut author P. G. Bell is as fun as it is full of heart, and the first book of a trilogy.
A train that travels through impossible places. A boy trapped in a snow globe. And a girl who’s about to go on the adventure of a lifetime.
The Impossible Postal Express is no ordinary train. It’s a troll-operated delivery service that runs everywhere from ocean-bottom shipwrecks, to Trollville, to space.
But when this impossible train comes roaring through Suzy’s living room, her world turns upside down. After sneaking on board, Suzy suddenly finds herself Deputy Post Master aboard the train, and faced with her first delivery—to the evil Lady Crepuscula.
Then, the package itself begs Suzy not to deliver him. A talking snow globe, Frederick has information Crepuscula could use to take over the entire Union of Impossible Places. But when protecting Frederick means putting her friends in danger, Suzy has to make a difficult choice—with the fate of the entire Union at stake.