The path is evidently incorrect. Your file "C\spectra\graphene9p11h_UV.out" should be "C:\spectra\graphene9p11h_UV.out"
]]>Have you checked section 4.11.6 of the manual? It is very easy, in the file (multiple.txt) you only need to set the path of each ORCA TDDFT output file and corresponding legend text. e.g.
examples\spectra\indigo\ZINDO.out ZINDO
examples\spectra\indigo\TD-PBE0.out TD-PBE0/6-31G*
examples\spectra\indigo\TD-PBE0_TZVP.out TD-PBE0/def-TZVP
Then use the multiple.txt as input file, and plot spectrum with usual steps, you will find all spectrum curves are simultaneously plotted on the same graph.
Best wishes,
Tian Lu