Engine/Clutch/Powertrain

When my engine is in neutral it reaches red line with no problem. It also has power in first and second gear. The problem happens when i am driving up a long incline, I will be in third or fourth gear flooring the gas but my rpm’s wont go up and neither will my speed. What might be causing this and what parts would I have to change to fix this problem? I drive a 2020 Jeep JLU manual 6 Speed.