I have wiring running from my house to garage for power.
At some point in the wire it is broken. How do I find that point of the
Break?

With an instrument called a TDR or Time Domain Reflectometer. You should know the total length of the cable.

TDR Tutorial - Power Applications

Other choices exist if it's not buried deep and not in a metallic conduit. You could use a non-contact voltage detector and run it along the length of non-metalic cconduit.

Check the end points first for loose connections.