As of question writing, these are the 7 states that are listed as "safe" or "solid" Democratic seats on Wikipedia by all four ratings columns.

How many of them will the Democrats actually win?

Based on a consensus of credible reporting, or certified results if consensus reporting is not available prior to that. Counting independent senators who have announced they intend to caucus with the Democrats.

See also:
/EvanDaniel/how-many-safe-senate-seats-will-rep