Migrating a mongo db with same names


I have a mongo db on a raspberry pi and another one on my local pc. Both collections are structured in the same way (in terms of db(-names) and collections(-names), but filled with totally different (and non-overlapping) data. I would like to migrate the db from my pi to the local pc by first creating a backup on a an external harddrive from the pi, then connecting the harddrive to my local pc and restoring the db there, following the commands outlined here: How To Back Up, Restore, and Migrate a MongoDB Database on Ubuntu 14.04 | DigitalOcean. When creating the backup on the harddrive, how can I change the names of the dbs / collections? I am afraid that when I restore the data on my local pc, due to the same namings, the existing data will be overwritten. Or does mongodb automatically integrate the backup’d db into the existing one, if the names are the same? Still it would be better for me to have at least a new db created on the local pc, which is called “db_name-pi” instead of “db_name” and exists in parallel to the pi.