Converting text field to Note without losing data

Hi,

I have a custom list, for which I have created custom site column, custom content type using the elements.xml. The list contains few text fields.

There are around 200+ entries in the list. I need to change few of the columns to "Note" type.

Is it possible to change the existing site column to a "Note" field without the data being disturbed.

If yes, how to achieve this programmatically?

Thanks