hi samir,
with powershell, we can use the following command to find the sharepoint groups a user belongs to within a site collection.
get-spouser -site https://contoso.sharepoint.com/sites/finance -loginname *** Email address is removed for privacy *** | fl
in sharepoint online webpage, we can find the group information by checking the user’s permissions to a site collection. go to a site collection, then click gear icon > site settings > site permissions > check permissions.
regards,
jiaxing bian