You mean how to equip your ship?
That depends on what you want to do. Trade? Combat? Exploration? A little of everything (for which the Mk III is one of the best ships)?
Here is my current config, that is still work in progress:
https://coriolis.io/outfit/cobra_mk...2ov62f.Iw1-kA==.Aw1-kA==?bn=Zakk Cobra Mk III
Tonight, I will upgrade my power plant from 4B to 4A. After that, I will save up for upgrading both thrusters and FSD to 4A as well.
I have not finally decided yet what to with my shield generators. Last night, I found bi-weave 4C generators by chance, had never heard of bi-weave before.
Basically, it means you give up overall shield strength, but gain faster shield regeneration.
It's great for those interdictions where I decide to accept the fight. It's not soo great for interdictions when I decide to run away, and would thus like my shields to last as long as possible. OTOH, with bi-weave 4C instead of regular 4A shields, I can run away faster.
Another module decision I'm undecided on is fuel scoop vs. planetary surface scanner. I only have room for one of them, as I'm not ready to sacrifice cargo capacity. Surface scanner means more credits for my exploration data. Fuel scoop means no fuel stops on longer journeys. I frequently switch between both modules, can't really decide which one to keep. No matter which one I have installed, I always start missing the other one immediately.