I would guess 2 and1/2 turns out. Get it to go and then adjust it.

run the screw in till it bottoms out ,DON'T tighten it you can bend or break the needle.then back off 1 and 1/2 turns crank it and run the screw in or out till you get optimal performance

I don't specifically know, but you can adjust your carb while it's running to whatever makes it idle correctly. It's very easy to do, there are two thumb-screws, just toy with them.

This is an old engine that is subject to wear in the carburetor. The venturi vibrates on the main nozzle and makes adjustments difficult. The throttle shaft wears and causes lean and/or overspeeding.
Set the bottom screw at 1 1/2 turn and top screw at 1 3/4 to start. If this doesnt help, you will need to check the carb. Any Briggs dealer can get you a repair manual.

One common problem with adjusting the “mixture screw” is that sometimes / often the screw is turned too far in (clockwise) to its seat. When this happens, the soft metal (often aluminum) of the mixture screw develops a shoulder of sorts making further adjustments very difficult.

As you attempt to increase the air / fuel mixture by “unscrewing” the mixture screw, the mixture rapidly goes from too lean (not enough gasoline in the mix) to too rich (too much gas in the mix). This is the result of the mixture needle loosing its smooth taper.

I’d consider starting the “tune-up” procedure by removing the mixture screw to insure it’s in good condition.

Good Luck!