Active job

Replace carpet on 4-6 steps minimum

I have worn out carpet on my stairs and want to replace with some matching carpet that has been taken out from someone else's house so is second hand. Currently my stairs have a separate piece for each step rather than a continuous piece. I don't know whether it's better to replace it all (if I have sufficient with one complete piece) or each step individually. There are definitely 4 steps I would like replaced as a minimum. I do not have any underlay though so that would need to be purchased. One section of my hallway I am wanting removed and replaced with tiles which I have listed as a separate job.