Hexadecimal to Decimal

Question

Hi,

 

I am able to fetch the string from a machine in hexadecimal form that is as follows: 7E 1B 4B 00 00 08 00 00 00 AA 00 00 00 02 00 02 00 02 00 02 00 00 00 00 00 00 00 00 20 7D  . Now I want to convert it in decimal form in which fir st 4 bits represent  one data and so on. I am new to C#. May I know how can i go about it.