Hi @Amrou_Abas,
Welcome to Neurostars. I’m in the same boat as you. See my question here. Did you figure out how to convert your nii/nii.gz files to BIDS and also create subject specific JSON Sidecars and TSV files.
My post: No DICOMs only Nii files available--creating JSON Sidecars and TSV Files
Thanks.
–Subbi M.