commerce cart block with drupal theme
Edit your cart view and under Advanced, Theming: Information, click on Information and you will see this:



For template file name you want to use the last suggested name, (which I underlined for you) that way it only affects this specific view and not others. 

Now that you have a name, click on the blue link and copy all the code in there and paste it into your template file and modify as you wish. 

Remember to flush the cache to see changes or you could click the Rescan template files button