Battery of tests. There are a battery of tests that are used by professionals to determine learning style and ability. Psycho-educational, learning achievement, & social tests are standard in children. Most school systems offer these through a child study team assessment. Neurodevelopmental testing can precede or follow these tests depending on severity of the problem.
To get tested. To get tested for a learning disabilty mild or severe you need to find two or three good psychologists in your area who do this work regularly and ask them. The mildness ofmthe disability does not mean it will cost les it could cost more. Mild ld may be harder to pinpoint and may take more time to find. A related question is why are your trying to find this ld? What difficulty does it present?