Hi.
I have a crawlspace that’s attached to the part of the house from 1900s. There are two access to it, one from the basement and the other from the outside. The outside access used to be a vent. Couple of years ago, we laid down a thin layer of concrete on the floor and closed the outside access. I was thinking of laying a 6 mil vapor barrier down. Based on the pictures attached, how far up should the concrete blocks should I go? 
As you can see in the pictures, on the cinder blocks, there are cores (open holes), should those be covered so there’s no vapor transfer?
How should these be filled or covered?  Maybe sand or foam or just cement mixture?

Thank you!