Question about ModularCable RJ11 6P/4C - 69872

Unfortunately, that's not so easy. Do you still have the old cable? Look at the two plugs from the front and from above: 4 places (3 partitions) 4 pins 4 cable is old RJ10 4p4c (4 pins 4 connected); 6 places (5 partitions) 2 pins in the middle 2 cable is normal RJ11 6p2c; 6 places 4 pins 4 cable is RJ11 6p4c, also known as RJ14. There are also mixed forms of cables, e.g. one side RJ10 and the other

RJ11, depending on the sockets on the device and on the telephone socket. Under Wikipedia "RJ plug connection" you will find the corresponding diagrams. Good luck, greetings Alexander