It’s very unlikely you’ll get that kind of information for one of these. You don’t really get that level of engineering and quality control in $6 hobby spec motor.
The fastest way to get that information will be to buy one and measure it. Just use a lab power supply to drive it, and tie a string with a small weight to a pulley or rope spool on the output. Power in = Volts=Current. Power out = Weight times lifting speed.
Efficiency = Power out / Power in.
