How to get deleted photos

Also check the Photos app/application for a Recently Deleted album.

If this is on a device and you weren't syncing photos with iCloud, do you have a backup you can restore from? Restoring from a backup erases all data currently on your device. Any data newer than when the backup was made will be erased. A restore is an all or nothing restore. You can't access a backup and only restore certain files.

Backup - Restore your device from an iCloud or iTunes backup.    

If this is on a computer, do you have a backup you can restore from?

From iCloud? The best way to recover them is to use a computer. On a computer, sign in to iCloud.com using Safari and your Apple ID. Then, click on Photos. Near the left top on your screen you'll see Recently Deleted. Click this tab and you'll see which photos can be recovered. If you select one or more of them, a Recover tab will appear. Click it and the selected photos will be restored to iCloud Photos. To download them to your computer, use Download iCloud photos and videos  https://support.apple.com/en-us/HT209454