The countries clash in a potential Pool D decider at Tokyo Stadium on Sunday.
Wales have beaten Australia once in the last 14 attempts, although that rare victory did come when they last met during the 2018 autumn Tests.
Wing North was among a number of Wales players involved that November afternoon who are set to feature this weekend.
And if the Six Nations champions can deliver a repeat result, then it would put them on a possible quarter-final course to meet potentially France or Argentina.
With Uruguay recording a stunning upset win against Fiji, it means Sunday’s victors would have one foot in the last eight.
“They are a tough beast to beat,” North said. “They have skills from numbers 1-15, physicality and speed. We have to be on the money straight from the off, concentration from minute one and expect the unexpected.
“They have so many good players and trick plays, and we have to be on our mettle.
“The form Australia are carrying into this, they have grown as a team again and are playing some unbelievable rugby.
“They have got threats of physicality, speed, aerial threats as well. The form they are bringing in is impressive. We have to go up a gear.
“We know we have to be at our best. The second half (against Georgia on Monday) we were nowhere near where we need to be to beat Australia.”
Wales opened their World Cup campaign with a 43-14 victory over Georgia, when they secured a try-scoring bonus point during a dominant display in the first 40 minutes.
They went off the boil after that, but still showed enough to suggest it could be a tournament when Wales feature as major contenders.
North added: “We expected physicality (against Georgia) and started strongly, but we should have turned up the pace a little more in the first half.
“You always need one bang-out to get your lungs working at this humidity and temperature, and understanding how the ball handles in this temperature, too. It’s quite interesting.
“That first half showed the intensity we wanted to go with. The second half we lost our way a bit and maybe came off the gas a bit. Maybe we should have turned it up a bit more.”
Wales head coach Warren Gatland is due to name his team for the Australia game on Friday.
Changes are likely to be at a minimum – if any – following the Georgia encounter, although prop Nicky Smith and back-row forward Ross Moriarty could come into Gatland’s selection equation.
Both players were on the bench against Georgia in Toyota City.
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