How do I figure out my door latch and strike plate alignment
Put something on the latch that will make a mark - wet ink, paint, possibly even chalk, crayon or graphite from a pencil. Close the door and look at the mark, or if feeling like that will be too messy, tape paper over the strike area and then close the door with the prepared latch.

If you have old, now uncommon, typing materials, "carbon paper" could be laid on top of the paper on the jamb/latch and that would allow the latch to make a mark without having anything directly applied to it. But the stuff is so rare now I don't assume you can easily get it.

In the vast majority of cases the strike needs to move down, unless something like tightening the hinge screws will bring the door back up. Doors tend to sag under the influence of gravity. But if the house itself has shifted, some other direction may be required.