The two timeframes matter enormously, because iOS has a built in safety net with a clock and past it the recovery gets harder, so recent first then the older batch:

The recent ones, the Recently Deleted album: iOS keeps deleted photos in Photos, Albums, Recently Deleted for 30 days before permanent deletion, so recently deleted photos are simply sitting there waiting. Open it, select your photos, Recover and they return to the library. This solves the great majority of deleted photo panics, the safety net doing its job and it is always the first place to look.

The older batch past 30 days, the harder case, in order of hope: an iCloud Photos backup, check photos on iCloud.com or another device signed into the same Apple ID, since the photos may still live in iCloud or on another synced device even if gone from the phone. An iTunes or Finder backup of the iPhone from before the deletion, restorable to recover the photos as they were at backup time, though restoring replaces current data so it is a whole device rollback rather than picking photos out. And an iCloud Backup similarly, restorable to a point before deletion.

The backup restore caveat worth stating: restoring an old iPhone backup to get old photos overwrites everything on the phone with that backup's state, losing anything since, so it is a real tradeoff rather than a simple recovery, best done by restoring to a spare device or after backing up the current state first, extracting the photos, then restoring current.

The honest boundary past all backups: photos deleted past 30 days with no iCloud copy and no backup are genuinely very hard to recover, since iOS does not leave them accessible the way a computer drive does and third party iPhone recovery tools have limited success against modern iOS encryption. The realistic hopes are the safety net and the backups, which is why the recent batch is likely saved and the older one depends entirely on whether a backup or iCloud copy exists. Check every synced device and iCloud before concluding the older ones are gone.