Please teach me how to uninstall my mongodb in my virtualbox(ubuntu).

I tried these command and nothing was removed : 

```
sudo apt-get purge mongodb mongodb-clients mongodb-server mongodb-dev
sudo apt-get purge mongodb-10gen
sudo apt-get autoremove

```

It still exists.
I type `mongod --version` it shows `db version v2.6.1`

Update:

I want to remove it and then install it again:

I tried the following 4 commands - 

```
sudo apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv 7F0CEB10
echo 'deb http://downloads-distro.mongodb.org/repo/ubuntu-upstart dist 10gen' | sudo tee /etc/apt/sources.list.d/mongodb.list
sudo apt-get update
sudo apt-get install mongodb-org

```

then
 sudo service mongod start

and type `mongo` there is error:

```
MongoDB shell version: 2.6.4
connecting to: test
2014-09-02T21:27:10.390+0800 warning: Failed to connect to 127.0.0.1:27017, reason: errno:111     Connection refused
2014-09-02T21:27:10.392+0800 Error: couldn't connect to server 127.0.0.1:27017 (127.0.0.1), connection attempt failed at src/mongo/shell/mongo.js:146
exception: connect failed

```

Did I miss something?
Please help me. Thank you!!