lost my iphone can i retrieve photos

If you had iCloud Photos turned on before the phone was lost, you can use any internet browser and log into www.icloud.com and go to the Photos app there. Also, if you turn on iCloud Photos on a replacement device, the photos will automatically sync with it. See: Set up and use iCloud Photos - Apple Support

If you didn't have iCloud Photos turned on but do have an iCloud backup, if you use the backup to setup a replacement iPhone, iCloud, the photos will be included. You cannot otherwise view the contents of the backup. Restore your iPhone, iPad, or iPod touch from a backup - Apple Support