I am not able to find
Harmonica VOICE in PSR E423. Can someone help if it has got different name in keyboard?
As per GM1 instrument sound specification, it should be instrument# 23. See here: https://www.midi.org/specifications-old/item/gm-level-1-sound-set
It's Voice 38 (In the Accordion section).
Here's the voice list for that specific keyboard; https://www.manualslib.com/manual/474736/Yamaha-Psr-E423.html
If a voice isn't in the main voice list, check the XGlite voices, which adhere more closely to the GM specification. According to the data list for this model, you'll find the harmonica as voice #327, which is MSB000 LSB000 PC023 in the XGlite voices as expected.