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The 23-year-old Wales international played for Scarlets for three years before joining Saints in 2013.
"I'm quite excited. It's a place I've got fond memories of, I've got some good friends down there," he said.
"For me it's a difficult one but we go there with a purpose for a win and a good performance."
He added to BBC Radio Northampton: "I've spoken to a few boys, I'll catch up with them after the game, it's nice to be back in Wales and hopefully a good opportunity to chase some points."
Northampton, second in Pool Three on 14 points, must beat Scarlets to stand any chance of reaching the last eight.
The Welsh club go into the game on the back of a 64-14 defeat at Racing 92 - their heaviest loss in the competition.
North has only scored two tries for Saints this season, and with the club fifth in the Premiership he said he was unhappy with his form.
"We're not performing as well we'd hoped," he said. "We've lacked a bit of go forward initially to put us on the front foot in the right areas and I think we've lacked a bit of composure in attack.
"For me personally it's been a bit of a frustrating few weeks. I'm there to do a job and if I'm unable to do that I get pretty restless and annoyed, but hopefully they'll be like buses."
Northampton Saints wing George North says he is looking forward to returning to Scarlets for the first time in the European Champions Cup on Saturday.