do I use PwnageTool to jailbreak it?

[kidwithdimples]

This 3GS is already jailbroken with blackra1n on 3.1

I want to jailbreak to 4.1 (or should I do 4.2?)

Version: 3.1 (7C144)
Serial Number: (first 5) 84937
Model: MC135LL
Modem Firmware: 05.11.07

can someone tell me the steps?

 

[PsstGreek]

This 3GS is already jailbroken with blackra1n on 3.1

I want to jailbreak to 4.1 (or should I do 4.2?)

Version: 3.1 (7C144)
Serial Number: (first 5) 84937
Model: MC135LL
Modem Firmware: 05.11.07

can someone tell me the steps?

Yes. Here's a guide on how to use PwnageTool to upgrade to 4.1 http://iclarified.com/entry/index.php?enid=12349

 

[Applejuiced]

You cant do 4.2 yet
Create a custom 4.1 ipsw with pwnage.

 

[Carlanga]

4.1 w/ PwnageTool, follow the instructions that the other member linked...
You could also wait until 4.2 gets released on who knows when in november and then wait for a new jb and unlock...