How do I find out what bootloader my 3GS has?

It is 3.1.3 and 5.12.01

Go to settings>general>about>model

If your model number starts with 'MC' then you have the new iboot on 3gs.

Ok, right on, ty.

Mine starts with "MB". So what does that mean?

Best Regards,

Todd.

You should have the old boot. Can always double check by putting phone in dfu mode, connect via USB to pc and check in device manager>apple mobile device driver> choose device instance path in the dropdown box, at the end of the string that is displayed will tell you the boot version

iBoot-359.3.2 is new boot
iBoot-359.3 is old boot.

Or you can use idetector from

Ih8sn0w.com/index.php/products/view/idetector.snow