A crowd of 26,923 saw the win against League Two Northampton Town.
The Magpies’ reward will be another home tie next month against Sheffield Wednesday at St James’ Park.
McClaren: “To get almost 27,000 was a great crowd.
“They have probably gone away – like me – and been pleased with the attacking side of it.
“There were some great deliveries and that is going to be vital.
“You can have people who are the best at heading in the world but it’s no good if the delivery isn’t right.
“Florian can score and assist and he showed what he can do.
“This was always going to be a difficult game.
“We started well and should have had three or four before half-time.
“We started well in the second half and overall it was a professional job.
“It’s nice win and score a few goals.”