Dear friend!
Its very easy to transfer contact from k750i to nokia mobile as i recently have transfered my contacts from k750i to nokia 5800XM.
1. First of all, get backup of your k750i contacts in Microsoft Outlook using SonyEricson PC suite (if you are using MS Outlook then use some other application that can store contacts on you PC).
2. After completing the above step, use Nokia Ovi Suite to synchronise stored contacts (on PC) with your nokia device.
Thants All and Enjoy.