City host the Toffees in the second leg of their semi-final on Wednesday needing to overcome a 2-1 deficit to claim a place in next month's Wembley final.
It is the third meeting between the two clubs in three weeks, after they also played out a goalless draw in the Barclays Premier League, and Pellegrini is hopeful of getting the upper hand this time.
The Chilean said: "I am sure if we repeat what we did against Everton here in the last game in the Premier League, especially the last 45 minutes, we are going to score goals.
"But it's very important to concentrate on defending because they have very dangerous attacking players - Ross Barkley, (Romelu) Lukaku, (Gerard) Deulofeu - difficult players to stop.
"We must be a very balanced team but not change our style of what is the best way to win."
The match at the recently-expanded 55,000-capacity Etihad Stadium is not yet a sell-out but, with 48,000 tickets sold as of Tuesday, the attendance will still be City's largest for a domestic cup tie since 1981
If the crowd goes above 50,000, as the club hope, it will be City's biggest cup attendance for 41 years.
Pellegrini said: "I'm sure that we're going to have the support of the fans we have in every game here.
"Of course it's asking a lot of supporters to support every game, but normally here in England the stadiums are always full for different reasons."