A 9:1 system is simply a 3:1 system with a second 3:1 system put onto the end of the first 3:1. I recommend using a release hitch on this sytem, as you can build up significant tension using a 9:1 system, especially with more than one person pulling on it.

It should be noted, however, that this is a 9:1 system when friction is ignored. That is allright when you use pulleys instead of carabiners, but carabiners introduce a significant amount of friction. This system generates a lot more tension than a 3:1 system, but it is not truly a 9:1 system. To find out what it actually is, you would have to measure the force you pull on the rope and compare that to the tension produced on the line.

Start out with a 3:1 system with a release hitch.

Clip a second carabiner into the anchor.

Place a prusik onto the end of the 3:1 system. Run the end of the 3:1 system through the carabiner at the anchor, and clip it into the prusik. This creates a secondary 3:1 system pulling on the original 3:1 system, for an overall 9:1 mechanical advantage. (See comments above regarding friction.)

When the prusik reaches the carabiner, simply slide it back out the rope and you can tension the system more.