Migrating contents to a new template

[Garnier Garnier]

Hi Listers,
 
Am using Framemaker 7.0
 
I was using a specific template for all the books. 
 
Now provided with a new set of templates (nothing matches with the earlier template) and expected to move all contents (30 books with multiple chapters and on an average each book contains about 500 pages). Any suggestions as to what would be the ideal method to migrate to the new template?
 
B/R
 
Garnier