First off, Jump is not a game mode. It's just a way of life for some people. You dont have a Jump mode, only pong_nokill 1.
To change the game mode type into your console window:
newmap <map> <variable>
Replace <map> with a map, for example shock.
Replace <variable> with a variable, see below.
VARIABLES:
DM - Deathmatch
TDM - Team Deathmatch
ELIM - Elimination
1FLAG - Single Flag Mode
CTF - Capture the Flag
SIEGE - Siege Mode
KOTH - King of the Hill
PONG - Soccer Mode
Replace
newmap <map> <variable>
with
newmap shock 1flag
*THATS AN EXAMPLE. PLEASE DO CHANGE THEM TO WHATEVER YOU WANT*