Without knowing the specifics of the office layout it’s impossible to come up with any real numbers.
Will you be using an IDF closet, or will all the switches be in one place? Will you be using copper or fiber to connect the switches? If copper then you’ll want to us Cat 6 cable.
As the switches are only 10/100 for the users you will want at least Cat 5E cables. If you plan on upgrading to Gig at any point you’ll want Cat 6 cable. As for length that will all depend on how large the office is.