I think the most important part is to make sure you are listening to your body and recovering on your easy days. If you have a pretty good idea of what your race pace is, there are some online calculators out there (such as Jack Daniels VDOT Running calculator) which will calculate all of your estimated training paces based on your race pace, and vice versa.
Of course, this is also just an approximation. Another option is to use a heart rate monitor. This Runner’s World article recommends 65 to 70 percent of maximum heart rate, or 10k pace plus 2 minutes for easy days. I hope you find this information helpful!