You can only clone one test case at a time. 
         
         
         
            - 
               Select More Options
                   for the test case that you want to
                  duplicate, and then Clone. for the test case that you want to
                  duplicate, and then Clone.The Clone panel appears.
                
- 
                You can rename the test case and select the information that you want to
                  clone:
               
               
                  
                  - 
                     Assignment to requirements
                     
                  
- 
                     Documents
                     
                  
- 
                     Labels
                     
                  
 
                  
                  Manual steps, custom field definitions, and custom field values are also
                     cloned if they exist.
                   
 
- 
               Select Confirm to clone the test case.
               
               The Test case will be cloned in the background message
                  appears.
                
A clone of the test case is created, with a different Id.
            
            
            
            Note: 
               
               
                  
                  - Automation information isn't
                     cloned.
                  
- Assignments to external
                     requirements aren't cloned.