Translation:We know how many centimeters one meter has.
i guess it depends on how you frame your sentence. if you say "we know how many centimetres one meter HAS" it is perfectly alright as "has" refers to the one meter. Alternately you could also say "we know how many centimetres does one meter have". "have" in this case is referring to the multiple centimetres
The 3rd person of the verb Have in present simple is conjugated as Has. The 3rd person of the verb Do in present simple is conjugated as Does. When in a question verb Do proceeds Have then the conjugation in 3rd person goes to the first one. The verb Have stays as it is. So if: -The meter Has 100 centimeters -How many centimeters Does a meter Have?