The car starts but when I press the gas pedal the car does not move, why?

The first thing we need to do it check the transmission fluid because if it is low there will be no hydraulic pressure which will cause the transmission to act the way you have described.

Here is a generic guide and instruction for your car in the images below and what type of fluid your transmission needs as well.

https://www.2carpros.com/articles/how-to-check-and-add-transmission-fluid

Also do the reverse lights work when in reverse? If not, the gear range sensor sounds like it is bad which will cause the same issue. Check out this guide:

https://www.2carpros.com/articles/automatic-transmission-problems

Fluid Types

Automatic Transmission Fluid .................... Mopar ATF +4

NOTE: Dextron II fluid IS NOT recommended. Clutch chatter can result from the use of improper fluid.
Capacities

42RLE

Service Fill .................... 4.0 Qt (3.8L)

Overhaul Fill .................... 17.6 pts (8.3L)*

545RFE

Service Fill

2WD .................... 11 pts. (5.2L)

4WD .................... .................... 13 pts. (6.2L)

Overhaul Fill .................... 28.0 pts (13.33L)*

*Note: Dry fill capacity Depending on type and size of internal cooler, length and inside diameter of cooler lines, or use of an auxiliary cooler, these figures may vary.

The dipstick is on the passenger's side near the firewall, here is the location of the gear range sensor as well.

The Transmission Range Sensor (TRS) is part of the solenoid module, which is mounted to the top of the valve body inside the transmission.

Let me know what you find.