There are a number of sources that you can use in your research for the Model UN simulation, all of which are in this research guide.
In order to build a country profile, look at these sources:
You can also find books on your country using books and articles from the online catalog and databases.
To find out where your country stands on any particular issue, you can look at the resolutions passed by the United Nations Security Council. These resolutions are available from the UNSC's website. Here are instructions for accessing these resolutions: