On my iDevices, I have over 500 photos. On "My Photo Stream" on my PC, I see only 38. How do I get the rest of them?

On my iDevices, I have over 500 photos. On "My Photo Stream" on my PC, I see only 38. How do I get the rest of them?

Searching the forum, I found five or so people with similar problems, and in all of that, no solution. I am about to assume that iCloud Photo does not work on Windows, but decided to post here first. Any insight would be welcome. Thanks.