Check the Recently Deleted folder in your gallery/photos app
Open the Photos/Gallery app → Albums/Utilities → Recently Deleted → select photos → Restore
If you use Google Photos: open Google Photos → Trash → select photos → Restore
If you use iCloud Photos: go to iCloud.com/photos or Photos app → Recently Deleted → Restore
If you use OneDrive: open OneDrive → Recycle bin → select photos → Restore
Check if the photos were synced to another device/account (same cloud account) and restore there
If you backed up to a computer (Windows File History/Backup or macOS Time Machine), restore from the backup
If you have an SD card or external storage, stop using it and check for recovery options
Use reputable photo recovery software on the storage device (after stopping further writes)
If the device is damaged or the storage is failing, contact a professional data recovery service