I have to replace a brake caliper on my trailer,it’s the second farthest from my EOH pump do you think I will have to bleed all 4 brakes or just that one?

Id just bleed those 2..........the one you are replacing and the furthest one

You should just need to bleed the one if that's the only one that was "open".
You're lucky with just one. I replaced 1 last year, just replaced the other 5 two weeks ago. I hate salt water. Lol.

That’s what I thought I just wasn’t sure.

not knowing how the lines are plumbed its a guess by us