Here are some resources to help you both learn more about and practice multiplying and dividing fractions and mixed numbers. Choose whichever resource you think will help you the most, or work through all of them, whatever works best for you.
Now that you've spent some more time learning and practicing, here are some additional pretests that you can take.
After each pretest, check to see how many you get right. If you get 6 or more correct, then move on to another section. If you get fewer than 6 correct, practice some more using the above links, then try another pretest.