This Code Gist Will Move the Fields in this order, First Name, Last Name, Email Address and Password When using the Code to Generate a username at PMPro checkout from email for users and hiding the username field with CSS - Links for this below

pmpro_move_name_fields.php

<?php // Do not Copy This Line

/**
 * Add the following code to your PMPro Customizations Plugin - https://www.paidmembershipspro.com/create-a-plugin-for-pmpro-customizations/
 */

function pmpro_move_name_fields() {
	global $pmpro_pages;
		?>
		<script>
			jQuery( '.pmpro_checkout-field-bemail' ).prependTo( '.pmpro_checkout-field-password' );
			jQuery( '.pmpro_checkout-field-firstname' ).prependTo( '.pmpro_checkout-field-password' );
			jQuery( '.pmpro_checkout-field-lastname' ).appendTo( '.pmpro_checkout-field-firstname' );
		</script>
		<?php
}
add_action( 'wp_footer', 'pmpro_move_name_fields' );