It is unusual to have a mildew build up in this type of dishwasher. Here are some tips that may help:
Check the drain configuration of your dishwasher according to the installation instructions. A drain problem could cause water to siphon back into the dishwasher and could cause mildew problems.
Make sure that you are using rinse aid. This will help the water drain off of the dishes.
If you are not using a heated drying cycle, try using the heat to dry out the tub better.
Try cracking open the door between uses to circulate some air through the dishwasher between cycles.
Make sure that the dishwasher is filling properly. It should fill to within 1/4" to just touching the bottom of the heating element.
To remove the mildew, you may need to run an empty wash cycle with liquid chlorine bleach added. Run a second empty cycle after this to completely rinse all bleach out of the dishwasher. If this does not remove the mildew, then you may need to wipe down the inside of the dishwasher with a strong solution of liquid chlorine bleach and water. Then you can run an empty cycle with bleach and another empty cycle with water to rinse the dishwasher out.
A failure in the pump could prevent your dishwasher from spraying properly. If you suspect a problem in the pump area of your dishwasher, you can use the procedure in this link of a previous answer to access and check the sump area:
How do I clean the filter on my dishwasher?
If you need more help with this problem, resubmit your question with additional details.