In the battle with One for All, All Might ran 5 kms in 30 seconds, that means running at 600 km/h. But All for One told him he was slow. Are there references how fast was All Might in his prime, at least an estimate?
That's actually the only information we have on All-Might's speed.
That scene you're referring to occurred in Chapter 90, which tells us that All-Might ran 5 kilometers in just 30 seconds, giving him a speed of about 600km/hr.
If I recall correctly, this is currently the best estimate we have of All-Might's speed at his prime, because we know he's faster than that. Only thing to do is wait for new chapters that give additional information.
All for One says "it's only five km from the bar to here and yet it was at least thirty seconds after I sent the Nomu that you arrived" meaning it took him 30 seconds to defeat the Nomu and then make his way to the bar.
For the record, he fought the Nomu for about 20 seconds and talked to Endeavor for about 6 seconds. Now you should be able to get a more accurate speed