If you want to control graphics then likely you want to use a graphics procedure like Proc SGPLOT.
The Histogram statement will create histograms.
You could control the range of values for the axis with a yaxis and xaxis statements though you should likely use the Histogram SCALE=Percent option for the y values in your histogram .
You need to describe what you mean by "adjust the unit of the histogram". If you mean number of tick marks or groups then that might be the NBINS option on a histogram statement.