DQA: Question about IPv6 subnets and routing

So I'm not a complete idiot, but networking has never been my strongest suite.

Question: ISP gave us a \64 subnet. The route is from ::1 to ::2. Do I have the ability to assign \56 subnets from an L3 switch as is or do I have to go back to the ISP with the requested routes for each \56?

I have a Cisco L3 SmartSwitch and a Sonicwall TZ400 I'm working with currently.

I'm not asking for the answer, just if I'm on the right track or not. And if anyone has like a link or video of someone visually explaining this stuff that they could recommend, that would be even better.