I'm really stuck on what should be a simple bit of maths

I have a known flow rate eg 1 ltr hr. That equates to a flow in mls of 0.27778 (Lhr/3600)

I know the area if the ID of the tube eg 2mm ID = 3.14159 (π*R^2)

Now if you do the maths for 1mm h and 1mm r you get 3.14159 mm2 convert to ml = mm2 / 1000 = 0.00314159

Then I get lost going from that to working out what the speed of flow through said ID tube is in mm/s

Many thanks if you can help

Cheers Tim