It’s really not all that difficult. These were designed to run off 3.7V Just set that voltage on your power supply and note the current.

From that current, you can calculate the resistor needed in series for any higher voltage.

 

Thank you all for your help.

 

The graph is a bit of a puzzle because it does not have much of a curve. Of course this is with the included resistors which does affect the flatness. So I concur with "Y" that around 30 to 35mA?? or right around 3 volts across the LEDs is reasonable. But a small bit more can deliver a lot more light.