How much steerer tube length do I need on my suspension fork
No, there is no way to look up the lengths of tubes. According to quick web search, both bikes have 1 1/8 threadless headsets, so that is the diameter you should shop for.

What you can do is measure the head tube of the frame, add a couple of centimeters for headset, around 5 centimeters for the stem and room for enough spacers to get the handlebars at the height you want.

Typically threadless forks come with very long steerer tube to fit the largest frames, and you are supposed to cut it to correct length yourself. When in doubt, leave some extra length and fill it with spacers until you are sure that you want to keep the bars at lower height.