Data copy from one attribute to other

I am looking a way to copy present data from page two attribute to page three attribute.

To give back ground -

We are customising all parts sub class and adding new parts sub class, now we need to move few page two attributes to page three. But presently legacy parts sub class objects have data populated to the page two attributes and i need to keep the same data in page three. Also there will not be any changes in attribute type and list values with new Page Three.

Any help is much appreciated.

Regards,

Sagar