Run the following task, assume that input file is H2CO.inp and output file is H2CO.out

! PBE0 def2-SVP
%tddft
  tprint 1E-8
end
*xyz 0 1
C                  0.00000000    0.00000000   -0.52887900
H                  0.00000000    0.93777000   -1.12367000
O                  0.00000000    0.00000000    0.67757700
H                  0.00000000   -0.93777000   -1.12367000
*

Then run this command to obtain H2CO.molden.input:
orca_2mkl H2CO -molden

Load H2CO.molden.input into Multiwfn, and input
18
13
H2CO.out
1  //The excited state of interest

Now you have NO_0001.mwfn in current folder, which records natural orbitals of S1 state, and can be used as input file of Multiwfn for wavefunction analysis on the S1 state.

If you want to convert it to .wfx format, boot up Multiwfn and load NO_0001.mwfn, then input
100
2
4
S1.wfx

Now you have S1.wfx in current folder, which may be used in other code to perform wavefunction analysis for S1 state.