Off the top of my head,
We cruise at FL240 or 250, the Indicated Airspeed will be around 245-250 knots, this gives a true Airspeed around 360 Knots or ~M.59. It varies a little bit on weight and ISA deviation. This is using high speed cruise, which we use most of the time unless we have good tailwinds or are ahead of schedule when we will then use intermediate speed cruise.
If you need any tech info on the aircraft systems
SmartCockpit - Dash-8 400
is a good website.
If you need anything else, just ask.