I have found this on internet:

from dbruntime.dbutils import FileInfo

def get_size_of_path(path):

  return sum([file.size for file in get_all_files_in_path(path)])

def get_all_files_in_path(path, verbose=False):

  nodes_new = []

  nodes_new = dbutils.fs.ls(path)

  files = []

  while len(nodes_new) > 0:

    current_nodes = nodes_new

    nodes_new = []

    for node in current_nodes:

      if verbose:

        print(f"Processing {node.path}")

      children = dbutils.fs.ls(node.path)

      for child in children:

        if child.size == 0 and child.path != node.path:

          nodes_new.append(child)

        elif child.path != node.path:

          files.append(child)

  return files

path = "mnt/silver/delta/yourfolder/"

print(f"Size of {path} in gb: {get_size_of_path(path) / 1024 / 1024 / 1024}")

And worked perfectly.