hyphens - a ten-year period of documenting....?

1. 
   

   This book is the first volume and part of a ten-year period of..

   
   


2. 
   

   This book is the first volume and part of a ten years period of..

   
   



3. 
   

   This book is the first volume and part of the ten year period of..

   
   

Which is correct?