You can use /users/{ids}/associated
Try it for your network account
Returns all of a user's associated accounts, given their account_ids in {ids}.
{ids} can contain up to 100 semicolon delimited ids, to find ids programatically look for account_id on user objects.
You can filter the network_users returned by this method with the types parameter. Specify, semicolon delimited, main_site or meta_site to filter by site.
This method returns a list of network_users.