What is your problem?

If you have the string "$0#1", then that is already stored in memory as 0x24302331 - in fact, as 0x24 0x30 0x23 0x31.
You already have it - you don't need to convert anything!

If you mean you want to take the byte value 0x24 (or 00100100 in binary, or 36 in decimal, or '$' as an ASCII-coded character) and display it as "24" (the character '2' followed by the character '4'), then see my earlier post, Apply a little thought, and apply the same technique in reverse!

Or just use (s)printf, if you're in 'C'

Or, as has already been said, see the myriad other times this same question has been asked!