Pella casement window with a failed mechanism

I have a casement window with a failed mechanism- the piece that's supposed to glide along the bottom of the window frame has detached from the window. I can't seem even to close it by hand (without the crank)- it might be frozen.

I thought it was a Pella window (because other windows in the house are), but now I'm not sure. The frame is made of wood. Can you help me figure out what I need to buy to fix this? I've attached some photos.

Many thanks!