The Magpies take on the Premier League International Cup holders in the last four of this year's competition, with a 7pm (BST) kick-off at St. James' Park.
Newcastle beat Sparta Prague and PSV in their way to qualifying as runners-up behind Liverpool in Group A, but Porto - who thrashed Sunderland 5-0 in last year's final - are expected to be a far tougher proposition.
But 22-year-old defender Gillesphey told nufc.co.uk: "We're looking forward to it. It'll be a good game for the lads at St. James', especially against a team as good as FC Porto. It'll be a good experience.
"We've come up against Sparta Prague and PSV already and they all go about things in a different way, with different cultures, which makes for a interesting games - and hopefully it'll be another good one.
"It'll be good for the lads; for a few lads who won't be here next season, it's a chance for other people to watch them and maybe have a little look at them, and it's good for the lads who are staying to prove themselves.
"It puts a good foundation for them for the start of next season."
Gillesphey has been a regular for United's second-string this season, having spent the previous two campaigns on loan with Carlisle United, where he amassed a total of 55 league appearances as well a further eight in cup competitions.
There, he faced the likes of Adebayo Akinfenwa and Kevin Ellison but admits that coming up against some of Portugal's most promising young attacking talent is likely to be a different type of challenge.
"Porto will try and keep the ball and pass it, whereas when you're playing in League Two it's slightly different - a bit more physical," he said.
"It'll be a good test. We need to stay compact, because their attacking players will be good. I'm looking forward to it."
Newcastle have struggled in Premier League 2 this season, but have saved their best form for the cups. They reached the quarter-finals of the Premier League Cup and are into the final of the Techflow Marine Northumberland Senior Cup next month.
When asked why United had fared so much better in knockout tournaments, Ashington-born Gillesphey admitted: "I don't know, to be fair.
"Maybe in the league, we've had a different team most weeks - whether that's because of injuries, or the first team need players or whatever, but once you get going in the cup you want to go all the way and it gives you confidence.
"If there's as many at St. James' as there was at Sunderland in the last round, it'll be a good atmosphere and I'm pretty sure it'll help the lads play that extra bit better."
A result must be achieved on the night, with extra time and penalties if required.
Admission on Thursday night will be via the East Stand, and is free to season ticket holders and members, otherwise it's £3 for adults and £1 concessions.
The game will also be shown live on NUFC TV, with former Newcastle goalkeeper Steve Harper joining John Middleton in the commentary box. Coverage starts from 6.55pm (BST).
