To get access to the ScanNet scans please refer to ScanNet Official Repo for getting the download instructions. you will need to download the following files for each scan.

*.aggregation.json
*.txt, 
*_vh_clean_2.0.010000.segs.json
*_vh_clean_2.ply
*_vh_clean_2.labels.ply

For Nr3d, you need to preprocess only _00 ScanNet scenes but for sr3d you need to add the --process-only-zero-view false argument

cd referit3d/scripts
python prepare_scannet_data.py -top-scan-dir path_to_scans_dir -top-save-dir save_dir

This scripts will load for each scan its point-clouds with annotations and pickle the results in a single file. Use the default options for nr3d. you can safely ignore the scene0009_00 warning.