Here is the Fanuc Ladder Software for editing ladder software.
You will need some additional Fanuc hardware to be able to change the ladder though (eg,Fanuc eprom blower; RS232 cables; PMC RAM etc...)
If you use following software you can use any commercial eprom reader/writer to do fanuc
pmc compiler and discompilier
https://www.cncb3h.com/fladder_e.htm
pmc compiler and discompilier
https://www.cncb3h.com/fladder_e.htm