How long it will will take for acute and chronic leukemia to develop in the body before they can be found on cbc or show symptoms,,,, months or years?

Indeterminate. It is not feasible to say, for a normal person, how long it will take for the person to develop leukemia. Vast majority of the people never get one.
For good health - Have a diet rich in fresh vegetables, fruits, whole grains, milk and milk products, nuts, beans, legumes, lentils and small amounts of lean meats. Avoid saturated fats. Drink enough water daily, so that your urine is mostly colorless. Exercise at least 150 minutes/week and increase the intensity of exercise gradually. Do not use tobacco, alcohol, weed or street drugs in any form.
Practice safe sex, if you have sex.