Installing/Upgrading MongoDB on a Raspberry Pi (ARM based processor).
Currently, there is no publicly available MongoDB 3.0+ distribution for the Raspberry Pi.
I found instructions on how to install MongoDB 3.0.9 from Andy's MongoDB 3.0.9 binaries for Raspberry Pi 2 & 3 (Jessie) blog.
While his blog tells you how to completely install MongoDB, I prefer a one line approach to install programs, so it can be more automated.
I have developed a script that will pull his files and automatically do the install on Raspbian Stretch and Jessie.
The only command that you will have to execute is this:
curl -sL https://raw.githubusercontent.com/lashower/MongoPi/master/install.sh | bash -
This script has been tested on a Raspberry Pi 3 running Raspbian Stretch.