Elements start out using Top and Left keyframes to express their position. Motion Paths are a different system that use bézier curves, and thus replace the explicit top/left values.
In most cases, Hype won’t give a warning about the conversion as the action tends to be pretty explicit by dragging the path of the object to make a curve. However there are some circumstances where you may have initiated using motion paths and Hype can’t do a “clean” conversion. The most typical case is using a non-default transform origin on the element.
The easiest way to reverse if you didn’t intend to make a motion path is of course to undo .
Beyond this, you can hit the motion path button in the property list to convert or un-convert. The Edit > Use Motion Paths / Remove Motion Paths menu item will also do it.
Motion path mode:
Top/Left keyframe mode:
The toggle is the little icon next to the keyframe button.
Note that it is a transformation, so you may lose some of the data from how it was originally. The warning dialog in particular is trying to point out that you will be losing information in the conversion, and thus also can’t go back to top/left keyframes in the exact same state.