The info in your ban link says it all; you had a modified client in Survival and were banned for it. However, I do think there’s a really good chance that you forgot you even did it considering that this ban is pretty old at this point, being about a year and 9 months old.
Can you read the rules and quote the rule(s) you broke? Do this in a new reply, don’t edit your appeal. If you do not know how to quote the rules, read the guide How to quote the rules.
If you do not identify the right rule(s) that you broke or you do not know which ones you broke, I can make it clear.