2 different Apple ID passwords - I want just 1, the same on all devices

Somehow - maybe when my computer was being serviced - the password for my Apple ID when logging in from my Mac was changed to my computer login password - let's call it Apple Password #2. However, the password for my Apple ID when logging in anywhere else - iPhone or iPad - is still the original Apple ID password - let's call it Apple Password #1. HOW can I rectify it so that I am using just ONE Apple ID password on all devices?

I really don't want to be using my computer login password as my Apple ID password.

I'm terrified of messing with my Apple ID because if things get screwed up I'm screwed.