Sync Member registration form with Contacts?

So assuming that your custom fields are all lower case, then your code should be something like this.

import wixUsers from 'wix-users';
import wixWindow from 'wix-window';
import wixLocation from 'wix-location';

$w.onReady(function () {
    
    $w("#submitButton").onClick( (event) => {
        
   let email = $w("#email1").value;
   let password = $w("#password").value;
   let first = $w("#firstName").value;
   let last = $w("#lastName").value;
   let position = $w("#position").value;
   let phone = $w("#phone").value;
   let howTheyHeard = $w("#dropdown1").value;
   let organization = $w("#organization").value;
   let address = $w("#address").value;
   let gradeLevel = $w("#gradeLevel").value;
   let comments = $w("#moreinfo").value;

   wixUsers.register(email, password, {
       contactInfo: {
        "firstName": firstName,
        "lastName": lastName,
        "email": email,
        "position": position,
        "phone": phone,
        "how they heard": howTheyHeard,
        "organization": organization,
        "address": address,
        "grade level": gradeLevel,
        "comments": comments
       }
      } )
      .then( (result) => {
        let resultStatus = result.status;
  wixWindow.lightbox.close();
  wixLocation.to("/member/me"); 
      } );     
    } );
    
});