Coefficient Scaling of IIR filter to obtain unity gain response
It's important to specify at which frequency you want unity gain. But assuming you mean DC ($\omega=0$), because that filter has a low pass characteristic, the DC gain of an IIR filter is given by
$$G_{DC}=\frac{\sum_kb[k]}{\sum_ka[k]}\tag{1}$$
It's also common to normalize the denominator coefficients such that $a[0]=1$. In your example that would give
a = [1.00000  -0.29240   0.10849]
and
b = [0.00000   131163547.59967]
Finally, normalizing by the DC gain $(1)$ will give you a filter with unity gain at DC. This leaves the denominator coefficients unchanged, and the new normalized numerator coefficients are given by
b = [0.00000   0.81609]