Microsoft 365 IT Support and set up with outlook/teams etc

I now have 2 Microsoft 365 subscriptions
one with 123reg that i purchased with my domain
and one straight from microsoft

the one from 123reg I use for my business and I have now moved my domain to 20i... but microsoft 365 business is still there.

So I would like the following.

1-a Freelancer to merge/migrate the two subscriptions into one WHILE
2. Ensure to not lose any data from either account.
3. then set up the login details and admin access for microsoft 365 in a way that I don't run into any login issues when trying to reset or change settings in the future.

Also. after I transferred my domain name and made the same email alias on the new host, I entered the new imap details into outlook and although it worked, I now keep getting prompts from windows to enter password for Microsoft exchange?. I want my email migrated smoothly with ALL My old emails and merged into one email as now I have two inbox accounts with the same name on outlook, one for the old and one for the new.

Ultimately I just need someone to set up my microsoft 365

I need my email