Converting Drupal Content Types
Have a look at the Node Convert module.

Node Convert adds a menu tab &quot;Convert&quot; on the node view page, i.e. node/1/convert, which gives the ability of converting the node from its current node type to another node type. Also it gives the ability of transfering all the custom CCK field values of the current node type to the destination CCK fields, or discard them. As of 5.x-1.4 you can bulk convert many nodes of the same type, to another one that can be accesed in Administer → Content → Convert Nodes.
The module has been tested on converting node types with the following CCK fields:

Text
Number
Image
Node reference
User reference
Link
Date
Datestamp
Email
Audio
Video


Here is the documentation for the module: https://drupal.org/node/291564