Deadpanda

umm i tried changing the version of tekkit but it still didn't work, how can i see what version my server is?

i have a 1.2.5 vanilla minecraft server and i want it to be a tekkit server, i've tried just to copy the world file to the new tekkit server while erasing both the old tekkit world file and nether and end files. but everytime i try to log in to the server says "must have forge build #136+" and i cant seem to figure out why. i know it have something to do with the version of the server not matching but how can i change that? and btw i haven't updated the server to the newest version, i know that because i stoped playing on the server about 3 months ago