We're nowhere, folks.
Literally speaking, if we imagined the setting of each metaphor, it takes us to Africa, where there would be majestic elephants roaming out on plains, back to suburban America and its rows of oversized houses, into a surreal garden where melons can stroll, and then back into the wild of fruit, ivory and timbers.
Then it takes us into the kitchen, where bread is rising, and perhaps onto a city street, where a rich person has just gotten fresh new money from the bank and is off spending it in fancy stores. Then we jump to a farm, where we'd be likely to find pregnant cows and bags of apples. We end up, finally, on a train. Interestingly, this poem ends with a journey. When we stop reading, our speaker is still moving, as is our literal setting.
But here's the thing. Even though it's fun to hop around to all of these different, imaginative places, changing our setting from metaphor to metaphor, beneath the surface, there is the real setting surrounding the pregnant woman this poem is describing. We have very little that lets us know what this setting is like, but we can imagine the setting that would surround a pregnant woman in the late 1950s, which is when this poem was written.
That wasn't an easy time to be knocked up, because it wasn't an easy time to be a woman. This real life pregnant woman is probably not on a train at all, but stuck in one place, too pregnant to travel. Yet she feels as if her life has boarded a train—she's stuck moving in one direction, the motherhood direction, whether she wants to jump off halfway through the journey or not.