I wonder if links from sites that are not indexed in Google can help my site in its ranking on Google?
They wont count at all until the site itself gets indexed - and who knows how quickly that will happen
They will not count. However, if the site owner is receiving web traffic, that could help increase your own.
they are useless , not indexed mean that this page is very lower traffic , still new with no page rank .
if the page you are interested in is not indexed, social bookmark it to increase its chances of being indexed so it will count in the end