Drop in the attachment that arrived from Google, Yahoo or Microsoft and read it as a table. Nothing is stored and no account is needed.
Search the mailbox in your DMARC record's rua= tag for
"Report domain". Google sends from noreply-dmarc-support@google.com,
Microsoft from dmarcreport@microsoft.com. The attachment is the report.
Then your domain either has no DMARC record or no rua tag.
Run the checker to find out which, in about a second.