I need to get a copy of 4.11, can't be any version higher. Hopefully can install it on Linux Mint 17.3.

it might be useful to say why

fyi - there was never a 4.11 version of ktorrent , the current version is 4.3.1

if you need an earlier version suggest you find a livecd and run or install it, if you want it to run in 17.3 you'd have to find the source and compile it assuming it could compile