fmri rest data without fieldmap or inverse acquisition

Dear colleagues. I am a predoctoral student at the University of Santiago de Compostela (USC). I am starting to work with resting data and unfortunately I have neither b0 inverse acquisition nor fieldmap. I would like to know if it is correct, in my situation, to use the CONN pre-processing step of "realignment and unwarp" . I already ran the following preprocessing (picture attached) and everything seems to be correct but I would like to make sure of the procedure used, as you can read, I am a beginner in this type of analysis. Any advice is welcome. Thank you very much in advance.

Benxa