Chris Hogg, who was named as United's under-23s head coach on Wednesday, will take charge of his first game with the young Magpies against their Iron counterparts at Whitley Park (kick-off 1pm GMT).
After five games in Group C, Newcastle currently sit in second place on eight points, four points above Hull City but McEntee is determined to secure a win in their final group fixture that would ultimately seal their place in the last 16, with United's second-string also bidding to continue their four-game unbeaten streak.
The teenage centre-back, who has represented Republic of Ireland at under-19 level, told nufc.co.uk: "It's a massive cup game for the squad because we need to have games to play for next month and it's a must win game for us because if Hull win their two games, we know we cannot draw so we are going into it trying to win.
"The wins and clean sheets have been massive for the team. It helps the team a lot when the back four are gelling together and keeping clean sheets, week in week out. We just have to try and continue that until the end of the season."
The two sides last met in a six-goal thriller back in November, with Newcastle's youngsters held to a 3-3 draw at The Sands Venue Stadium after squandering a two-goal lead in the closing stages.
Although Scunthorpe are yet to register a victory in the group stages, McEntee is fully focussed on the task ahead and believes his side cannot underestimate their Lincolnshire opponents.
"Scunthorpe aren't a bad team at all," the defender added. "We drew with them last time around and we played with ten men during the game. Ollie (Walters) went off injured and we had ran out of substitutes so we were all trying to work hard for each other.
"It didn't go for us that game as we conceded two late goals, which was disappointing to take as we worked so hard for the whole match.
"We have to make sure we put it in our own hands and not leave it up to any other teams because football can be a weird game. If we get a win, that's us sorted so that's what we'll be focussing on."
With the arrival of Hogg, McEntee believes the new coaching addition can only benefit the youngsters as they approach the final stages of the 2019/20 campaign.
The Irishman also highlighted his delight in featuring in United's Tyne-Wear derby win against Sunderland as the squad recorded a third successive win and clean sheet in all competitions.
He said: "It was an unbelievable experience playing at St. James' Park in a derby and the fans were amazing! I didn't expect it to be that loud in the stadium. There was a lot of supporters and it was a great win for us along with another clean sheet.
"We have had that mentality where we hate conceding goals. Everybody is staying compact and working for each other, which is really good.
"Now that the team is starting to gel together, anything is possible. We need to take it game by game and aim to win as many games as we can.
"It's probably the same at any club with a new coach. Everyone wants to impress him so the intensity in training will be lifted even more than it already has been in the past few weeks as the sessions have been great.
"Everyone's out to impress him because there's a lot of good players in this squad so we're just fighting for places at the moment."
Admission for Friday's Premier League Cup clash is priced at £3 for adults and £1 concessions. Entry is free for season ticket holders and Members.
