I have moved into this house and in the basement I noticed what I think is mold/mildew on the cinder blocks, however they were painted.I need to know is there any way for me to treat this issue & for it to work since they were already painted?

Sounds like the mold/mildew is coming from the inside, which probably resulted from dampness in general. Look closely at the floors and where anything touches the floor - to see if you can determine where the dampness/humidity is coming from.

Spray the mold with bleach and then after a day, carefully remove it with a sponge. Wear a mask to be safe.

Treat all areas the same way and make sure to treat areas as needed.

If you find that water is coming in through the block wall, then you need to remove the paint and treat the wall with something like Thoroseal - in the hopes that it will retard water from coming in. Additionally, inspect the exterior to be sure that 1) the gutters are properly draining water away from the building and 2) that there is not a low spot along that wall where water can settle.