Decimal to hexadecimal conversion is done through division.
Divide the decimal number by 16
Record the result and the remainder.
Stop the division when you have the result = 0
Now the remainders are what you need.
Write them out from bottom to top.
In a situation where you have "10,11,12,13,14 or 15" as remainders, replace them with hexadecimal alphabets(A,B,C,D,E,F)