Haha sorry I'm new here, I'll work on it. What level should I check the IVs at? I know one parent had five IVs and I used the destiny knot. But what nature would be best?
You can check IVs at level 1 since they are set and cannot be changed. You need to go to the IV judge. The IV judge is in a Pokemon Center at the Battle Resort, which is unlockable after beating the Pokemon League.
For a quick guide on IVs you can click here.
As for natures, you can just choose a nature from EV builds listed in places such as Smogon or even poke around the trade shops on this forum and see what kind of larvitars are being traded around.