IIR filter how to transform digital filter after cascading two filters

hi everyone , i am creating chebysev type 1 low pass filter order two and chebsev type 1 bandpass filter order 4 so i have to cascade them after i will use bilinear transformation to convert digital filter

1)after cascaded this filter how to get this filters numerator and denumerator values

2)i am using fvtool to display hcas filter but i saw it as normalized frequency how can I see time scale between [-0.5:0.5]

% chebysev type filter 1 low pass filter set to two

clear all

close all

n=2

fs=1000;

f=fs/2;

wp=300;

wn=wp/f;

rp=10;

ftype='low'

[b,a]=cheby1(n,rp,wn,ftype)

m=2048

freqz(b,a,[-0.5:1/m:0.5-1/m],1)

figure

%%%%for bandpass set to 4

n1=4

wn1=[wp/fs 480/fs]

f1type='bandpass'

[b1,a1]=cheby1(n1,rp,wn1,f1type)

freqz(b1,a1,[-0.5:1/m:0.5-1/m],1)

figure

%cascading

a=[1,-0.00133634481338596,0.723867172613969,0,0,0,0,0,0]

b=[0.136178018892628,0.272356037785256,0.136178018892628,0,0,0,0,0,0]

H1=dfilt.df2t(b,a);

H2=dfilt.df2t(b1,a1);

Hcas=dfilt.cascade(H1,H2)