All subscribers that have been added to your subscriber list can be found on your Subscribers page under All subscribers.
When you create a form or landing page to collect email addresses, you select a group into which subscribers of that form will be added. To find subscribers who were added to a specific group after completing a form:
Navigate to Subscribers.
Click on the Groups tab.
If you’re not sure which group you selected, follow these steps to find out:
Click on the title of your form or landing page.
Scroll down to where it says Subscribe to groups.
Here you will find the group(s) associated with that form. Click on the name of the group to open it.