Don’t use bleach. Bleach will kill the existing mold but won’t stop new mold from forming. For that you need to treat the fibers with disodiumoctaboratetetrahydrate. You can make this yourself. Get a roach powder that is mostly boric acid, mix one pound of this with a pound and a half borax powder.
Boil two gallons of water and mix in the powder. You will probably only need about a pint of this to treat the trunk and carpets of your vehicle. You can use the rest to treat any wood you have around the house. It stops rot and drives off termites and other insects.