Ran out of 30 minutes of editing time and don't remember all my latest changes so the entire corrected post is shown below. The preceding post needs to be deleted.
Where do the hot and neutral for the light fixture leave from?
Where do the hot and neutral of the power source come in?
A 3 way dimmer set generally has at least three wires going between the box with the main dimmer module and the box with the remote module: a hot line, a neutral line, and a single "traveler" or control line. (There may be other wires connected to the modules themselves.)
Usually it is possible to repurpose lines as needed and convert to a plain 3 way switch setup which requires two travelers and a common.
Label and unhook the incoming power cable. If lights or receptacles elsewhere in the house and unrelated to this 3 way controlled light stop working then there may be complications possibly making the conversion to plain 3 way switches impossible.
The conversion can make the total system non code compliant since there might no longer be a neutral at each switch location. (You could complete the project without anyone's being the wiser.)
Specifically, you need, among other things, at least two lines going from one switch location to the other and nowhere else. If either of these two consists of two "halves" spliced up in the light box, no third wire end may be attached to that splice. Ultimately these two wires will be attached to the traveler terminals of the new plain 3 way switches.
How the third wire is connected depends on where the power comes in, etc.
That means you need to find out what the wires are doing inside the walls.
Do not unhook wires without first labeling them. Save all parts you are removing until the project is finished and working.