Try this: if your hard requirement is THREE LEDs and the DC3-10 260 mA CC source.
(1) take each of the 3 LEDs and add a 25 ohm resistor in series. This will create a 3.5V drop at 20mA
(2) Wire these three LED sets in parallel. This creates a 3.5V drop at 60 mA
(3) Now you need in parallel 200 ma (200 + 60) at 3.5V which is 17.5 ohm BUT will require 0.7W power dissipation, so take 10 175 ohm 1/8 W resistors and place them in parallel to get 17.5 ohm 1.25W resistor.

 

Try this: if your hard requirement is THREE LEDs and the DC3-10 260 mA CC source.
(1) take each of the 3 LEDs and add a 25 ohm resistor in series. This will create a 3.5V drop at 20mA
(2) Wire these three LED sets in parallel. This creates a 3.5V drop at 60 mA
(3) Now you need in parallel 200 ma (200 + 60) at 3.5V which is 17.5 ohm BUT will require 0.7W power dissipation, so take 10 175 ohm 1/8 W resistors and place them in parallel to get 17.5 ohm 1.25W resistor.

Yes, that works. The resistor gets a bit warm, but it seems to operate just fine.

 

Good to hear. How did you get the 17.5 ohm resistor? Did you use 10 175 ohms in parallel or some other combination? The rational behind 10 was to distribute the thermal load and avoid running resistors over their thermal limit.

 

Yes, that works. The resistor gets a bit warm, but it seems to operate just fine.

It gets warm because you are using a supply that always supplies 260 mA and your LEDs meed only 60 mA and wasting 200mA. If you use an appropriate supply, it will barely get warm.

Just use a 9V constant voltage supply and put the 3 LEDs in series along with one resistor calculated to drop 3V at 20 mA, i.e. 150 Ohms. The resistor would only need to dissipate 60mW.

 

These LED packs and drivers are on top of the search list on AE. The LEDs are 20mA and most likely cool white or warm white (judging based on the semi-transparent bulb) and you need ~1.8V to get full brightness from them. You can solder them in series (cathode to anode) up to 11 and test it with that "19V no load" driver. Cathode is the shorter leg and its polarity is negative. If the brightness is too low, short out one LED at a time to get brightness without burning LEDs.
This is what "in series" mean
Driver's negative> short leg-long leg----(solder joint)-----short leg-long leg----(solder joint)-----short leg-long leg----(solder joint)-----.......