Questions: Are all of the backups of the 3 different iPhones on iCloud under the same Apple ID? Is the iCloud account still active?
If the answer to both of the above questions is a YES then the Photos, Contacts, Calendar items etc. should be the same across all three of those iPhones. If you used the previous backups to setup your iPhones, as you purchased them, then there should be one single valid backup which you can use to restore to a new iPhone.
It appears that you are planning to save the data to a PC. If that is the case then log in, using a PC, to ➔ www.icloud.com with the same Apple ID (iCloud ID) that you used in the past. Once you have successfully logged on then you can ➔ Begin Exporting/Archiving your Photos, Contacts, Calendar events, Notes, Reminders etc. to your PC.
Axel F.