How do I find the password for icloud mail?

iCloud mail uses your Apple ID and password.

iCloud uses your Apple ID and password. If you only have one Apple ID, it would be the same ID and password as you used to log into this forum. If you have another and have forgotten the ID or password, see the following:

If you forgot your Apple ID email address or phone number - Apple Support

or

If you forgot your Apple ID password - Apple Support