Space State & tf2ss Command Question

Hi every helper

i have a set of 2 equations and i want to reach the ss equation.

Note: D means d/dt & D2 means derivative of second order (d/dt)^2

Equation are

(1) : m1.D2y1 + k1.y1 + b1.(Dy1-Dy2) + k2.(y1-y2) + mu1.N1.Dy1 = F

(2) : m2.D2y2 + b2.Dy2 + mu2.N2.Dy2 - k2.(y1-y2)= 0

equation belongs to a mass-damper-spring system .

the space state variables are

Dy1

D2y1

DX

D2X

and X=y1-y2

How Should I reach to transfer function?

How Should I reach to ss?