Villa have won nine of their last 12 games – including three on the spin – to climb to fourth in the Championship table.
“Friday is a massive game,” Johnstone said.
“Coming off the back of three straight wins, hopefully they are more scared of us. It’s all about confidence.
“If you are full of confidence it is a different game. We will be up for it, hopefully we can get three points.”
Villa’s excellent run has seen them already reach the same number of away wins they managed last term – four – while Villa Park is starting to become a fortress again.
“It’s just football,” Johnstone said. “It was difficult at the start of the season but we put a few results together and it does give you confidence going into each game.
“Three points are all that matters. I’m glad we are winning both home and away.
“We are full of confidence at the moment. We have had three great results and are properly starting to gel together and grind results out.
“Last Tuesday night against Sunderland was difficult but we ground the result out and that is the main thing, getting three points.”