Importing from MSP - Mapping Columns

Hi,

I am trying to import a project from MSP into an existing WBS inside a project.

There is certain data which has been included within text columns 1,2 and 5 within project and when the import box pops up an option for field mapping is given. However the columns which I would like to map to are not there.

How do I go about extracing the data from the MSP text columns and putting it in the P3e columns?

Thanks in advance