Convert frequency response to impulse response
Here is a MATLAB example. Inefficient code but hopefully easy to read

%% Example: first order bandpass from 200 to 2000 Hz sampled at 44.1 kHz
n = 1024; % FFT length
fs = 44100; % sample rate
f0 = [200 2000]; % bandpass range
[b,a] = butter(1,2*f0/fs); % these are the difference equation coefficients
b0 = b(1); b1 = b(2); b2 = b(3);
a0 = a(1); a1 = a(2); a2 = a(3);  % for easier readability

% Step 1: build normalized frequency vector
om = 2*pi*(0:n/2)'/n;

% step 2: calculate the frequency response at every frequency
z = exp(j*om); % this is the "z" of the z-transform
% calculate the Z transform , 
H = (b0+ b1*z.^-1 + b2*z.^-2)./(a0+ a1*z.^-1 + a2*z.^-2);

% Step 3: make it conjugate symmetric
H = [H; conj(H(end-1:-1:2))];

% Step 4: inverse FFT
h = real(ifft(H));

% Step 5: verify against direct evaluation of the time domain difference equation
d0 = zeros(n,1); d0(1) = 1; % unit impulse
href = filter(b,a,d0);
err = 10*log10( sum((h-href).^2)./sum(href.^2));
fprintf('Error = %6.2f dB\n',err);