Split Sharepoint Content Database

[Barge77]

Hi Team

I have a single SharePoint content database (Sharepoint 2019 - On Premise) that is over 100 gig and I would like to split the SP sites between some new content
databases that I will make. I have created the new content databases but I have no idea on how to move the subsites to the new
content databases.

Based on research I have done it seems I need to
* Create Content Databases
* Create site collections in those databases
* Move sub collections into new site collections in the new databases.

Question 1 - are the above steps correct or do I have this wrong?
Question 2 - How in the heck do I move subsites out of the almost full content database, into new content Database? Do I move it to
the site collection in the new database? If so How?!?

Thankyou for your brainpower and help

[#2]

You cannot move existing subsites to new Content DB. A Web Application in SharePoint can have several Content Databases and what you can do as part of your Farm Design is to ensure each new Site Collection created can be linked to a single Content DB, but you cannot do that at the Subsite level