What are you trying to do?
Only the mobile operator has a need know this number and the UUID number of your device.
IMEI numbers are set in firmware and in most domains re-flashing an IMEI number is strictly illegal.
If you are waiting a legal unlock your carrier will request you confirm your IMEI number (AND they know using the tower triangulation where your phone is so don't make it up !) The IMEI number will be passed by your carrier to Apple.
Your carrier will notify you that your unlock request has been successfully registered on Apples server via text or email.
You then connect your phone to your PC/Mac. Launch iTunes and follow the unlock process.
THERE ARE NO other LEGAL reasons to mess with the IMEI/UUID codes.