Insert previous users into membership tables

I'm trying to do a bulk insert of data into the aspnet_Membership table. I have existing records from a previous version of the system I am re-building in asp.net. I've been researching and asking questions, but I am still missing something. What is the best way to do this? I believe I need to grab my previous table and iterate over each record and insert into the new membership table via the Membership.CreateUser method. So far I have been unable to make it work. My code so far in the on click event of a button is below. Any help would be appreciated.

using System.Web.Security;
using System.Data;
using System.Data.SqlClient;

protected void Import_Click(object sender, EventArgs e)

string connString = "data source=(local);Inital Catalog="Testing";Integrated Security=true;";
SqlConnection conn = new SqlConnection(connString);
SqlCommand cmd = new SqlCommand("Select UserN ...