3rd question - Skills Assessment - using web proxies

can somebody help figure out this problem I have been stuck for weeks?

Question: Once you decode the cookie, you will notice that it is only 31 characters long, which appears to be an md5 hash missing its last character. So, try to fuzz the last character of the decoded md5 cookie with all alphanumeric characters, while encoding each request with the encoding methods you identified above. (You may use the “alphanum-case.txt” wordlist from Seclist for the payload)