I don't know the brand Dondo used, but there are many "generic" versions of it , usually 4" or 6" long.
In photography the exposure is measured in F stops. From one stop to another you double or halve the amount of light that hits the film/sensor.
The three variables are ISO, aperture and shutter speed.
ISO : 50/100/200/400/800 ......( ISO is the "sensitivity" of the film or sensor . The higher the number the less light you need but the more grain/noise you get)
Aperture ( an iris will control this) F1/2/4/8 (but more commonly 1.4,2.8,5.6...) note that from F1 to F2 you have 2 full stops , so there are in between steps, IE F1.4/1.8/2/2.8/3.5....... with in lens apertures (DSLR) , or even more with in shutter (compact cameras) aperture blades.
F1 is the existing light, F2 is 1/4 of that.
Shutter speed 30/15/8...sec then 2/4/8/15/30/60/125.... fractions of a sec (125th) from 1/60th to 1/125th there is one stop (twice the shutter speed/half the light)
Digital compact camera usually have an Auto ISO setting , most will let you set that manually.
So......... to get a 3 sec exposure, drop the ISO to your lowest setting (usually 50 ) then select 3 sec( shutter priority) if you have that or just select a small aperture (Aperture priority , F11/16/22...) till the camera gives you the desired shutter speed .
If this does not make sense, please ask again