How to get photos transferred from old iPhone to my new iPhone?

did you set up the new phone by restoring from the backup from your previous phone?

Transfer data from your previous iOS or iPadOS device to your new iPhone, iPad, or iPod touch - Apple Support

If you created a backup of your old phone and restored the new phone with that backup, your photos should have come over. The only reason they would not have is if you were using iCloud photos on the old device. If that is the case, you would need to go to Settings>your Apple ID>iCloud>Photos and turn that switch on. Then make sure you are connected to a stable wi-fi and allow the photos to sync from iCloud. You can also log into iCloud on a computer and check to see if the photos are there. If not, then you may need to try to restore that last backup again.

I'm not sure why you refer to Optimized Storage. Did you log into iCloud on the computer and see if your photos are there? Do you still have the old phone you can check to see if the photos are there, and you could also create a new backup if necessary and restore that if the photos are not in iCloud.