import re
s=""""Заключение:
1
2
3
Подпись"""
print(re.search(r'(?m)^(\d[\d\r\n]*)^Подпись', s).group(1).split())
print(re.findall(r'(?m)^\d+(?=[\d\r\n]*^Подпись)', s))
aW1wb3J0IHJlCnM9IiIiItCX0LDQutC70Y7Rh9C10L3QuNC1OgoxCjIKMwrQn9C+0LTQv9C40YHRjCIiIgpwcmludChyZS5zZWFyY2gocicoP20pXihcZFtcZFxyXG5dKile0J/QvtC00L/QuNGB0YwnLCBzKS5ncm91cCgxKS5zcGxpdCgpKQpwcmludChyZS5maW5kYWxsKHInKD9tKV5cZCsoPz1bXGRcclxuXSpe0J/QvtC00L/QuNGB0YwpJywgcykp