Hey @Pulciu, I’ll try to help you with that!
I’m not sure how the curve looks like in your project, but if you select the MotionExtractorModifier in the Animation Data Modifier window, you should be able to simply type the bone name (foot__l and foot_r) and extract the curve. It’ll give you different values depending the settings you have, so could you share a screenshot of the curve you need?
This example is with the default options:
