low pass filter using matlab

hey guys i have original signal with 3023 hz frequency , after adding 128 zeros between samples , i want to create low pass filter half band or using FIRPM for filtering my signal_fir1 , how i can do it

f = 3023;

fac1=128

fs1 = 48000;

nT = [0:1/fs1:1];

signal = sin(2*pi*f*nT);

signal_fir1=zeros(1,fac1*length(signal));

signal_fir1([1:fac1:end])=signal;