Finding line and load when retrofitting a GFCI
It matters on a GFCI that the line is from the breaker and the load is the downstream devices. A non contact tester can identify the hot when they are disconnected from the existing outlet make sure to get the hot and neutral from the same incoming cable wired to the line side then the downstream outlets on the load. As you install the outlets make sure to use the labels that say no equipment ground and you will be good to go.