You'll need to establish the correct key names for both canpar and woocommerce, but for example, just making up key names here, do something like this:
If any conversions need to be done, do it before the $url assignment, using other variables to hold the converted values. You then would use cURL or similar to send the request and receive the returned values from the canpar site. Process the returned values as needed before returning the values yourself to the caller. This all would be inside a function called presumably from a woocommerce page that needed the data in the first place.
If you haven't yet, also read Writing a Plugin. I hope this all makes sense. Cheers.