T-Mobile Sidekick "whats sim number car" Questions

want to unlock my t-mobile sidekick slider forgot 3 # number code i did put on it what is the special code to enable to sim car to T-mobile sidekick slide?

...SIM card seated properly I turned the Dash on and left it cycling to drain the battery. My battery is old and I recharging it with the car charger gives it a hotter charge. I suspected the battery ...