4k7 is a very common way of writing 4.7 k(ohms) to avoid "losing" the decimal point if there is poor quality printing (or bad eyesight ).
But in that application (pullup for a pushbutton) almost any value from <1k to > 1M should work fine. I'd usually use the internal "Weak Pullup" (~33 k) in PICaxes which support the feature.