Super Admin user account appears to have been deleted from the database

Hello WP Support Community,

I've been asked to upgrade an old WPMU installation to WP Multisite and so far it has gone well, but I've been unable to log in as the Super Admin user to complete the process.

I checked the 'admin_user_id' record within the 'wp_sitemeta' table, but it was set to 1, and there is no record in the 'wp_users' table with an ID of 1.

I've been doing a bunch of research to try to figure out how to make my user account the Super Admin, but none of the suggested methods have worked.

First, I changed the 'admin_user_id' value to my user ID within the 'wp_sitemeta' table.

Then, I added my user account to the 'site_admins' record of the 'wp_sitemeta' table, being careful to follow the proper format.

Neither of those suggestions has done the trick. Now I can see the "Tools -> Sites" menu option in the admin nav bar, but when I try to access that page I get the "This admin screen is only site admins" message.

Can anybody recommend any additional steps that might be necessary in order to make my user account the Super Admin?

Thank you very much for your help.

Adam