Install MongoDB on Debian
To install specific version of mongodb you need to follow certain steps documented on MongoDB site:

In my opinion it includes: 

sudo apt-get install -y mongodb-org=3.0.1 mongodb-org-server=3.0.1 mongodb-org-shell=3.0.1 mongodb-org-mongos=3.0.1 mongodb-org-tools=3.0.1


You can opt for packages by omitting it from above list.

You can find detailed document here