Aerobic base -building effort is determined by heart rate, not cadence or speed.
You need a heart rate monitor and a fitness test to determine your anaerobic thresh hold. Strongly recommend Sigma Sport heart rate monitors.
Your metabolic level steady state (MLSS) is 10 beats below your AT. That is where you will develop the most base fastest.
How you acheive a specific cadence and speed are irrelevant in training. I like to acheive them by getting use out of, the gears on, my cog set that don't get used much the rest of the year.
Don't try to piece together a program off the internet. P.M. me and I'll help further.
"The field mouse is fast, Ricky, but the owl sees at night."
Grandpa Chip