The Bucks are welcoming Leyton Orient for the second leg of the FA Trophy semi-final, with the winner going onto Wembley for a chance of silverware.
Telford are 1-0 down after the first leg at Brisbane Road, Macauley Bonne the scorer, and a sell-out is expected as they aim to overturn that deficit.
“We really wanted the community to come out and back us, and they have done just that,” said an excited Cowan.
“The support for the first leg was unbelievable, and we’re going to need them to make themselves heard once again.
“It is going to be great to see the New Bucks Head packed out with supporters, and if we achieve the unachievable, they’ll be able to proudly say ‘I was there when Telford made it to Wembley’.
“That’s what we want. It’s a celebration, isn’t it?
“A celebration of what we have managed to achieve so far in the competition and in the league.
“It has been special already, but come down and celebrate with us, will us on, as we look to achieve the unachievable.”
Bonne struck in the 54th minute last weekend, but the Bucks were always in the game, as Andre Brown and Daniel Udoh both had chances to grab a leveller in the second half.
Reflecting on that game and what was learned, Cowan said: “Orient pretty much controlled the game at one point.
“The pitch was massive and they played the ball around really well.
“We lacked that control, and they were getting a bit of joy, but I didn’t want to force the issue too much.
“The key was staying in the game, which we did. Our substitutes came on and did well too.
“Andre held the ball up better up top, and Dom Smith made us more solid at the back, so that was pleasing.
“We’re pretty set on where we want to be, how we want to approach it.
“I watched a few Orient games before last week, so we knew plenty about them already, but the players are fully aware of what’s ahead of them now.”
He added: “It’s going to be a tough, but it’s one we’re thoroughly looking forward to. We can’t wait.”