Q: Batch rename and number photos?

In Photos you can batch rename all photo sto the same title, but without a running number.

You need an Apple Script to add a running counter.

See these user tips for scripts:

Batch Change Title to Text w/Padded Sequential No.

Batch Change Title to Capture Date-Description-Padded Sequential Number

You can during export - I am not aware of anyway to do it within Photos

LN