Replacing the ceiling fan/light with a ceiling light. The ceiling box has two sets of wires. One set has a yellow wire, white wire and black wire. The second set has a green wire, white wire and black wire. The ceiling fixture I am trying to attach has only three wires. Which wires do I attach? When someone tried in the past they could not get the light to to turn off and on.

All green or bare wires connect, all white/neutrals connect, and the black from the fixture I suspect will need to connect to the yellow, assuming the yellow is switched.

I tried connecting all the whites together, the two ground wires together and the one yellow wire from the ceiling box with the black wire from the light fixture. This left two remaining black wires from the ceiling. What do I do with the remaining black wires? When I did this the light did not turn on. In addition the two other kitchen lights no longer worked. The two other kitchen lights have separate swiched but are on the same outlet.

Do you have a voltage tester? You need to determine which wire, if any, is connected to a switch, and which wires are live constantly.

Otherwise I am just am just guessing.

No voltage meter

Then keep trying different combination is your only hope, assuming there is power at any of the wires, or there can be any other various problems.

Without a meter is like a doctor without a stethoscope.

I connected the two black wires form the ceiling together and all three lights worked. Thanks TK for your help.