Hello Admin M,
Thank you for posting your question in our community, kindly use the steps below:
In Yammer, click the Yammer settings icon., and then click Network Admin.
Click Export Users.
On the Export Users page, choose Export all users, and then click Export.
Save the exported file. The file is saved as a compressed file with a .zip file name extension.
Go to the location where you saved the compressed file and expand it.
You can also use the link below as it has steps with pictures:
https://learn.microsoft.com/en-us/yammer/manage-security-and-compliance/export-yammer-enterprise-data
Please let us know if you need further assistance.
Best Regards,
Asher