Hi I wish to use 5 slider pot with ESP32-PoE-ISO. WHhich Pin should I use? I am using only Ethernet (tcp server) and no other function
Just use the pins at the UEXT connector. There are 8 data pins available there (3 of them are multiplexed with the SD card, but you are not using SD card so it is fine).
Refer to the schematic and find UEXT1 connector and associated pins.