When you set the timing pictures of the camera systems in CMSV6, you will have timely snapshot of the cameras, and the time intervals can be set by your own. Pls check below rules: 

As above rules, the mdvr system will take a photo every 60 seconds. And after making the rule in cmsv6 , you need to assign the rule to the company or vehicles you managed. Pls check below:

And How can we check the snapshot from the cmsv6, where are the photo stored, in mdvr, computer or server? 

It is stored in the storage server of the cmsv6, so you can check the recording from the platform and see the photo file from the cmsv6 server, pls check the below photo for reference: 

For CMS Web API of timing snapshot, pls check the below rules: