The MongoDB Java developer course is good fun and not too difficult, and it will give you a good idea of how to use Java to interact with MongoDB. You have to write some Java code, mainly completing methods that they provide, but there's also a lot of work on MongoDB itself - JSON, data structures, indexing etc - and on the JavaScript-based MongoDB shell interface. Also, you might want to practice a bit using the Java
IDE before you start: they recommend IntelliJ and their sample code loads up nicely in IntelliJ, so it's easier to follow the Java examples if you're using the same tools.
If you're feeling ambitious, there's also the
Spring Data MongoDB project, which gives you a more abstract standardised interface to your database code, but if I were you I'd probably work through the basics with the MongoDB course first.
Anyway, MongoDB is good fun and very easy to get started with, so good luck with your project!