how do i know my photos are backed up to icloud from my phone

You can't see anything that is contained in your iCloud backup, you can only restore it to your device. Also, you shouldn't rely on iCloud to back up your photos. iCloud only backs up the photos in your camera roll at the time of the backup. However, if you delete photos from your phone and continue backing up, the backup containing the deleted photos will be overwritten by one that doesn't. And photo stream photos only remain in iCloud for 30 days.

Instead, import your photos to your computer while they are in your camera roll, as explained here: http://support.apple.com/kb/HT4083.