I used a pedometer many years ago. It didn’t hold my attention so I stopped. My iPhone counts steps also, but I don’t have my phone on me during half of my stepping.
The 10,000 step thing was a miscellaneous number with no real data, but it gives people a goal. A lot of people need or like to have that sort of thing. A goal or finish line to motivate them and feel accomplishment.
The Fitbit I guess is that thing that’s around your wrist like a watch? That sounds better so you don’t have to carry the pedometer with you.
My personality fits better with learning what my regular activities give me in terms of steps, like Zumba 5,000 steps, cleaning my house, 1,000 steps, etc.
There are studies on how many minutes/hours of exercise help extend age, Real Age looks at those and discusses them. Steps and time spent exercising have a correlation. Excessive high intensity exercise for extended periods actually seems to shorten life span, but I would guess you aren’t doing that.
If you have an iPhone you can use the app a few days to click your steps. Or, you can google and there is plenty of info on how many steps in particular exercises.