Hello utkuckmgl@gmail.com,
On the S32K148 there are 8 modules of FTM and output pins differs for each instance. So, if you need to choose the PE21,PE22 and PE23, you have to change the PWM module from module 0 to module 4.

Now, if you enable the first two pairs, (0-1) and (2-3) You will be able to directly select the required pins.

Hope this helps,
Marius