Error kspace

i want to simulate a box with fpp boundray condition but i have error for kspace style. What command should I use for Kspace?

The error you get is quite clear:

ERROR: Cannot use non-periodic boundaries with PPPM (src/KSPACE/pppm.cpp:208)

It’s way quicker to read the documentation than to ask a question on a forum and wait for some answer. If you want to simulate a slab, use kspace_modify to instruct LAMMPS to do so.