How to transfer a subdomain to a multisite with the same name?

Hi, I have 10 sub-domains with their own databases:
site1.domain.com
site2.domain.com
site10.domain.com

I will transform domain.com into a multisite with subdomains.

So, the multisites will have the same names i.e.
site1.domain.com
site2.domain.com
site10.domain.com

but they will share the same one dababase as the multisite feature.

How to transfer a subdomain to a multisite with the same name? Any plugin?

Cheers,

Vi