You'll probably want to read up on two's complement binary notation for signed integers, as well as binary-to-hex conversion.
The minimum value for an int is -2147483648. The bit
pattern for that number is
1000 0000 0000 0000 0000 0000 0000 0000
The hex equivalent to that bit pattern (1 hex digit per 4 bits) is
80000000
The maximum value for an int is 2147483647. The bit pattern for that number is
0111 1111 1111 1111 1111 1111 1111 1111
The hex equivalent to that bit pattern (1 hex digit per 4 bits) is
7FFFFFFF
Search the forum or google for "two's complement" and
you should be able to find some articles explaining how it works. You'll also want to get at least a little bit comfortable converting from binary to hex and from hex to binary, using a pencil and paper, or doing it in your head once you're used to it.