Convert a 3V battery powered device to USB power

Convert a 3V battery powered device to be USB powered:
https://www.instructables.com/community/How-do-I-convert-a-3V-battery-powered-device-to-be/
"I used an LM317T (purchased from radio shack) 2x100ohm 1/2watt resistor and one 40ohm 1/2 resistor. It produced 2.9v"
"The schematics can be found at quite a few places. Searching for LM317 and looking on wikipedia's website will show a few.   {Search for Schematic}
    https://www.alldatasheet.com/view.jsp?Searchword=LM317T
    https://duckduckgo.com/?q=LM317T+3v+circuit&t=ffab&iar=images&iax=images&ia=images
    https://www.circuitstoday.com/few-lm317-voltage-regulator-circuits

USB cables are supposed to have standardized conductor colors. Red+, Black-, White(data), Green(data), Shielding (ground). If you cut one end off of the cable you'll want to do the following:
1. Connect the red wire to the Vin pin on the LM317
2. Connect the r1 100ohm resistor to the Vout on the LM317
3. Connect the 100ohm resistor and the 40 ohm resistor to create r2.
4. Connect r2 to r1 and the Adj pin on the LM317
5. Connect r2 to the shielding/ground (Black?) of the USB cable
6. Add a lead from r1 for 3v output voltage."

How to Power Nearly Anything Off a USB Port:
https://www.instructables.com/id/How-to-power-nearly-anything-off-a-USB-port/
"... there should be 4 wires , you only need the red and black ones as they are the power ..."


Or just wire up a 3 volt Zener diode:
https://www.mouser.com/Semiconductors/Discrete-Semiconductors/Diodes-Rectifiers/Zener-Diodes/_/N-ax1mh?P=1yuq69l
    Mouser Part # 863-1N5333BG or 78-BZX55B3V3


USB Fan Project - Need Help Bringing Voltage Down from 5volts to 3volts...
https://www.electro-tech-online.com/threads/usb-fan-project-need-help-bringing-voltage-down-from-5volts-to-3volts.23572/


Powering electronics from the USB port (a little overkill for a simple battery powered device):
https://www.ti.com/lit/an/slyt118/slyt118.pdf?ts=1595605015624&ref_url=https%253A%252F%252Fwww.google.com%252F