Read the fine print. If the box and/or cassette sez C-41, then it is designed for the C-41 process. If it don't, then it ain't. Do any of the cassettes you have say C-41 on them?

Did you try looking on Ilford's Website for your answer before posting here? I can guarantee you that your answers are there. Ilford's C-41 monochrome film is called XP-2 Super.