The Export Customers module allows you to export your customers' data except passwords.
Indeed, it is not possible to export customers' passwords because they are encrypted and they cannot be extracted in plain format. This is a good thing to keep your site and your customers' data secure.
Store Commander application allows you to create and modify your customers' data in bulk with its integrated CSV import tool dedicated to customers' data except for passwords.
It is not possible to import customers' password for security reasons either. Your customers will need to reset their password to create a new one when they next log onto their account. Your webmaster could display a message on your website to inform your customers that their password needs to be reset (we do not have this Front Office functionality).