Here it is:
https://www.digikey.com/en/products/detail/onsemi/MOC70P1/402084
I don't think your replacement will work. The original's output is a phototransistor. I don't think you can replace it with a photodiode. Or you might find a replacement for the original part. Look on Digikey for:
photointerrupter - slot type - transistor output.
In any case, I think for all diodes the long lead is the anode.