Can I convert a single circuit with multiple lights/1 switch to control 1 light/switch
First step is to identify the switch that the power comes in to. The other two switches will just be farther down the line. Disconnect all of those switches and put wire nuts on all of the wires individually. On the first switch, figure out which wires go to the lights and wire nut those to the incoming power wires. Now none of the switches control anything and the lights should just be on.

You can then get something like X10 screw-in adapters for the light fixtures.