The semi-final was switched from Anfield to St Helens new Langtree Park stadium, and the striker is hoping supporters will make the short trip to cheer the Reds on as they bid to reach the prestigious final.
"Liverpool have the greatest fans in the world and we will need their help on the night," Ngoo told Liverpoolfc.tv.
"We know they will get behind us and hopefully we can do a good job on the night for them.
"To make the final would be fantastic. It's always a pleasure to play for Liverpool. It has a great history and to get to a final would be a great thing. We always take each game as it comes and we have to be at our best on the night."