Hi
In "Classic UI", if you are look at the assets on Digital Assets (http://localhost:4502/damadmin#/content/dam/), the you can not change the view from List to grid, there List view is the only option.
The thing which you are asking is in Touch ui, so if to go to touch ui and select Assets, then on top right there would be option of grid view or list view.
Link:- https://docs.adobe.com/docs/en/cq/5-6/touch-ui/touch-ui-structure.html
Else as mentioned by Tuhin, in classic ui, if you want to preview the assets, the the content finder is the option.
Link:- https://docs.adobe.com/docs/en/cq/5-6/dam/how_to_use_the_damfinder.html
Thanks and Regards
KautuK Sahni
Kautuk Sahni