How to recover photos from a stolen iPhone?

If you had iCloud Photos turned on, the photos would have automatically synced. If you aren't sure, use any internet browser and log into www.icloud.com and go to the Photos app there.

If the photos aren't there, then iCloud Photos wasn't on but you may have been automatically backing up to iCloud while the phone charged. You cannot view the contents of an iCloud Backup but you can use the backup to setup a new device. You can use information in the following support article to see what backups are currently in iCloud including the device name, date, and size of the backup. See the "Delete backups and turn off iCloud Backup for your device" section of Manage your iCloud storage - Apple Support (but don't delete the backup, just view the information about it).

This document has a list of things to do if your iPhone, iPad, or iPod touch is lost or stolen. --> If your iPhone, iPad, or iPod touch is lost or stolen - Apple Support

Log into icloud.com and open the Photos app. Do you see your photos there?