Edit: apparently this is a very common form of Japanese storytelling called an isekai. There are 8 billion people in this world, no idea can be original. And sometimes you miss out on things many other people know. I’m clearly one of today’s lucky 10000.
First assumption is an isekai into a world where all life is scaled up in size. Would gather up supplies and explore away from the train, heading for the base of a tree for shelter. If my theory is right, the train is a danger zone that will attract attention. If my theory is wrong, I can raid it for metal parts later
Of course, I would carry some of the steel from the train - Can use it to make sparks, crude weapons, etc.
Also would bring fabrics - Can’t be sure on water quality, and I know how to make a filter using bark, sand, gravel, and charcoal. Some fabric as a further filter would help out by preventing the components from slipping out of the hole in the bottom