Hi. I'm Brian and I'll try to help.
This forum is dedicated to problems using classic Outlook for Windows. There is a separate forum for Outlook on iOS. You should use that forum if you are using the Outlook for iOS app. If you are using a web browser like Safari on the iPad, then there is a separate forum for Outlook for the web.
Just FYI, outgoing mail uses the SMTP service, not the IMAP service. IMAP is for incoming mail. That said, the password is the same password you use to access the incoming server or to log into your Microsoft account with a web browser. Does that not work?