Hopefully this is what you're after. Assuming you have a list of users and you want to get the email of each user and send an email to all of them. Note that I'm not sure what your trigger is, so just using a Manual trigger in this example.
For this example, I have the following list.

See full flow below. I'll go into each of the actions.

Get items retrieves the items from the list. I'm not sure how many users you have subscribed. By default Get items only returns the first 100 rows. If you have more than this, you can set the Top Count to 5000 (max) to get up to 5000 rows.

Select extracts out the emails from each of the rows. My column is called Owner, so I would select Owner Email from the dynamic content.

Join uses the union expression to remove any duplicate emails that might be in the list. It then joins each of the emails with a semicolon.
union(body('Select'), body('Select'))

Send an email uses the output from Join to send an email to each of the users.

Some notes on this solution.
- Send an email can only send an email up to 500 users. If you have more than 500 users then let me know and can show you how to get around this limitation using chunking.
- This will allow users that have been sent the email to see all other users email addresses. If you didn't want this, and wanted to BCC all users instead, then let me know and can show how to do this (trick with getting around a blank To field).