Venice isn't the easiest city to navigate....but Venice Explorer makes it a snap.
Link to Venice Explorer
Once you go to the site there are many choices on the left, including a map search.
If you know the number and sestiere (district) that you are looking for you can find the exact location.
For instance....if you want to locate the Impronta Cafe....it's located in Dosoduro (sestiere) and the
number is 3815.
This certainly makes the search a lot easier.......