Casement window operator order

I bought a home with casement windows. 5 windows have broken gears on operating mechanisms. They are Truth EntryGard, and I need to learn how to measure them to order replacements. Assorted window sizes, so I need to know how to communicate the arm length to you.

- Home was new in 1997.
- I know that right and left are as viewed from outside.
- I know that all mechanisms, old and new, need to be cleaned and lubricated periodically.
- I am able to send photos of each mechanism
- I am aware that the short arm has an offset, and they all offset downwards.
- Local window contractor can install, but will not order parts, I have to get the parts

What else do I need to check or measure in order for you to recommend replacements and compose an order?

Update: Only 4 mechanisms need replacement. Photos attached.
I am aware that the roller is out of the track, I did that for visualization of the arm length