EXECUTION TIME FOR 30-40 MULTIPLE simultaneous USERS

Question

 I have a small windows application where the click on a button will display the  list of users in a datagrid  starting with a name that is entered in a textbox..

I would like to find out how much it takes if there are 30 users uses this search page simultaneously and find out the time it takes to fetch the results on to datagrid of my windows application.. 


sample code: 

private void btnseacrh_Click(object sender, EventArgs e)
  {
      var name=txttextbox.Text;

     var Resultdataset= Fecthresultfromdb(name);
     
 // retchresultfromdb method calls the database and fetches all the people whose name //starts with 'name' value entered in a textbox
     
    //finally result set is bind to datagrid for display

    datagrid.datasource=Resultdataset;

  }  
Now I would like to know if there are 30 users concurrently using this seacrher window,how much time it takes..This is one of non functional requirement that has to be met within 3 secs.

PLease tell what modifications i need to do..PLease share the modified code snippet as well.