I you have tagged them, svn co url://path/to/repo/tags/v2_0_1. If you have not, you will need to find from logs or something which precise revision corresponds to your version. (The /tags directory is not a feature of Subversion itself, but this is a common way to arrange things. To svn, tags and branches are just copies of individual revisions.)
Of course, in order for this to work, you need to obey some common conventions. A common workflow is to always have exactly three directories in the root of your repo; these are trunk, branches, and tags. You would always create new branches for development work from the head in trunk, merge to trunk when you are done, tag in tags when releasing. The command in each case is simply svn cp. See http://svnbook.red-bean.com/en/1.6/svn.ref.svn.c.copy.html