Have you read the book Understanding Exposure?
It is not a problem to ask on here but if you have some understanding of how shutter speed, aperture and ISO work to control exposure, and how you can catch action or prevent ( or create blurred backgrounds) it makes the explanations easier
To get all 3 dogs in focus you would need a fairly narrow aperture. this would create a deep depth of fies making all 3 in focus. however if because of narrowing the aperture, you are reducing exposure, camera may ( depending on seting) reduce shutter speed this will then " blur the movt of the running dog" this blur may be seen as a soft image which is so , not because of not being in focus, but because of movt
If you fix the shutter speed and have a wide aperture, the only thing to get a well exposed image is to increase the ISO
Unfortunately if you are so close to the first dog it may be difficult to get a deep DOF anyway as it depends on distance to subject, focal length used and also aperture
In short you would struggle to get all those 3 running as they are in foucs from your shooting point
You may have got it with it with flash but flash also has a maximum shutter speed you can use it with