Farming for prime parts

So i'm a pretty new player, and I would like to start farming for prime parts pretty soon since I know eventually they'll get their turn to go into the vault. I know most of the prime parts can only drop in T3 or T4 void missions though, and those have really high level enemies compared to what I've been fighting (first 6 or 7 planets.) So my question is, what would get me ready to farm for these prime parts? I have no idea how to gauge what lvl enemies I'm ready for, so is it more about the mods than anything? or what?