You've created a repository folder called
trunk with the first command (the
-r argument tells svnserve to set the given location as the root.), but this is just the filesystem location of the repository.
I believe svnserve will always seerve the repo as the root folder in the URL (I can't see any options in the man page for overriding this, anyway).
What I think you need to is to create and commit the
trunk folder into your empty repository (along with your branches and tags folders, should you desire them). My usual tactic is as follows:
On the Server:
svnnadmin create repo
svnserve -d -r repo/
On the Client:
svn co svn://domain.name/ repo/
mkdir branches tags trunk
svn add *
svn ci -m "Base directory structure"
svn://domain.name/trunk will be your repository trunk.