+- 5V differential ADC in the market?
Raspberry Pis do not come with integrated Analog-to-Digital Converters (ADCs).

You will have to buy an external board (HAT in the Raspberry Pi lingo) that provides that functionality when connected to your RPi 4b board. You will also have to make sure that this board accepts differential voltages in the voltage range you have. If the absolute value of any of the voltages is negative (relative to the board's ground), you may have a really hard time to find something that will work for you.

Places you can starting looking for the appropriate HAT for you:

Pinout.xyz

Sparkfun

Adafruit

UPDATE

Let me know if you’d like to build your own ADC circuit instead.