How do we fix the squeaky noise in stairs and put new stairs in?

I have carpet on my stairs and it’s not that bad but the stairs are extremely squeaky. We have stairs that lead to our ground floor basement and stairs that lead to our upstairs where the bedrooms are. Both are noisy but the ones going to the upstairs are the nosiest. If you are sleeping and someone comes downtown in the middle of the night it will wake you up. It is very difficult to get at these stairs to fix the noise so we are not sure what to do about it. Could use some DIY advise.

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