Czan, I suggest you read up on how a correct exposure is made. It's not a simple "set your camera to x" type of thing. To boil it down, there is an amount of light in a scene, and the proper capturing of that light requires you to set an ISO, shutter speed, and aperture and to understand the constraints that each of these has on the exposure as a whole.
But, to get you started in photographing water drops...
You want to freeze the action of the drop as it bounces off the surface of the liquid. In order to do this, you want to light the scene 100% with flash. (let's keep this easy and not introduce mixed lighting)
In order not to mix ambient lighting with flash lighting, you need to make sure that the ambient light is low. Leave enough light for you to move around in the room, but not much more.
Most of these types of photos are shot with off camera flash where the flash is set to a certain power. ISO is usually set to 100. Aperture is set for the depth of field that the photographer wants. This could be f/2 or f/16. It depends. But, to get you started, try using f/5.6 or f/8.
Now, the tricky part. Shutter speed. The fastest your camera will allow with 100% flash lighting is called the flash sync speed - and it's 1/200 of a second. This is perfectly fine to freeze a water drop.
However, using 1/200 will require you to time the shot far too accurately. You'll have to press the shutter release, the camera will have to drop the mirror, open the shutter, trigger the flash...all while you hope to capture a drop in air.
Instead, you are better off using Bulb mode. Bulb allows you to manually open and close the shutter, on your count. (keep in mind that we still want to avoid ambient lighting, so keep it short). But, the method here is: Trigger a Bulb exposure. This drops the mirror and opens the shutter - now the camera is just waiting for the flash to pop to expose the scene.
Drop your water droplet and manually trigger the flash when you want. The timing is extremely hard - but using this method, you only have to worry about when to pop the flash, as opposed to when to start the sequence of events listed above.
As soon as the flash has popped, stop the exposure. If you're working alone, you will need a remote shutter release. If you don't have one, you can try using a ~3 to 6 second exposure and hustling to do the rest.
You are using 100% flash here to light the scene. So, if it's too bright, decrease your flash power. If it's too dark, increase your flash power. If you've hit the limit on your flash power in either direction, you will have to either open the aperture (let in more flash) or close it (let in less flash). (You could also put diffusers in front of the flash to scatter and absorb some light if the flash is too bright [like a piece of paper] but keep in mind that this will greatly alter your lighting, for good or bad)
Here's a great article on more ways to light and expose these scenes.
Edit to add:
If you don't have a flash and can't follow the advice above, then you need to light the scene with as much light as you can. Get every lamp in the house. You need a shutter speed that is fast, 1/200 or faster. Set the aperture to obtain the depth of field that you want and get the ISO as low as you can, ideally, 100.
Again, I can't tell you exactly what settings to use because they are dependent on how much light you can add to the scene. Ideally, you would want ISO 100 with an aperture between f/2.8 and 11 (depends on the depth of field that you want) and a shutter speed at least 1/200.
As for timing, you'll need to fire the shot to capture the drop at exactly the right time. Look into "Mirror Lockup". This will allow you to set up the shot, lock the mirror up, and then trigger the exposure exactly when you want to. Again, a tripod and shutter release cable are invaluable here.
Trigger the mirror lock up, drop your water, and then trigger the exposure. Rinse and repeat.