Lost iPhone photos

Are you sure you didn’t do ANY of these ways of preserving photos?

• iCloud photo sync (check by logging in to https://icloud.com from a computer and click on Photos)
• iCloud backup
• iTunes backup
• Transfer your photos to your computer via USB cable
• Enabled Apple Photo Stream
• Sync to Google Photos
• Sync to some other photo archiving service such as Shutterfly
• Sync to Dropbox
• Sync to box.com
• back up to Livedrive
• Backup to any other backup or archiving service

If the answer is no to all of the above your photos are gone forever.

Then they were never in iCloud photos. Resetting an iPad will not delete anything from iCloud.

if you made iCloud backups you can still restore the backup. Backups are not the same as syncing. While both synced data and backups are both in iCloud they are unrelated.

Restore them from your last backup of them.

Have you logged in to icloud.com and checked to see if they are there? Are the photos still on your iPhone?