While they were hammered 7-2 in Barcelona in midweek, Elanga struck both of Newcastle's goals on the night.
The Swede said ahea of the St James' Park showdown: "It should give us motivation again, because we're (back) in the Premier League, and we want to keep the momentum we've had the last two games and building it.
"It's the biggest game of the season. We owe it to the fans as well, especially (from) the first time we played Sunderland this season. We need to use the energy and momentum we're building and make sure St. James' is bouncing."
On his Barca brace, Elanga also said: "Personally I'm really happy with that. I'm ambitious, though. I want those goals to turn to wins. I want to help the team get through to the next round. That's my ambition.
"Of course, I'm happy to score two goals here. From young, it's a dream come true to play at this stadium, so I'll try and take the momentum and try and make sure that Sunday gets even better."