Office Store

store.office.com
sellerdashboard.microsoft.com

msdn - jj220037
The information you submit via the dashboard should exactly match the information listed in your app manifest, including the name and version number.
screenshots must have file extension .png, jpg, .jpeg, or .gif, must be exactly 512 pixels wide and 384 pixels high, and be no larger than 300 KB.
When your app is approved by the Office Store team, it will be available for install via the Office Ribbon of the Office applications for which it was created.

Requires the developer to provide proof of identity to be able to submit add-ins
Supports a user review system.

96 x 96 logo
up to 5 screen shots (jpeg)
512w x 384h - less than 300KB

link - learn.microsoft.com/en-us/office/dev/store/add-in-submission-guide