Can I change my @me.com email address format?

See the instructions below.

Change your Apple ID (Be very aware of the restrictions here.) https://support.apple.com/en-us/HT202667

Before changing your Apple ID using a computer, sign out of all Apple  services that use your Apple ID. If you are going to use an iPhone, iPad, or iPod, then stay signed in with your Apple ID on only that device. This instruction is taken from the above document under the heading Before you change your Apple ID.

For sign out purposes, see Where can I use my Apple ID? https://support.apple.com/en-us/HT202659 “This list is provided for informational purposes only and is subject to change without notice. It's not intended to include every feature or service that uses Apple ID. Visit the Apple ID support page for more information.”

There may be some redundancy, but see What to do after you change your Apple ID or password 

 https://support.apple.com/en-us/HT204071

You can't change your Apple ID to newly created alias. The only aliases you can use are those that show a question mark on the right side.

From the article below.

When you use your @icloud.com email address

When you turn on iCloud email and choose your @icloud.com email address, your new @icloud.com email is assigned to your Apple ID as a login alias. To see the email addresses that are a login alias for your Apple ID, sign in to your Apple ID account page and click Edit in the Account section. Hover over the question mark icon  next to the desired email. If you see a message that says, "This is an alias of your Apple ID email address," that email should be eligible.

Change your Apple ID - Apple Support

Whilst you can not change the primary email address you can create aliases , subject to availability of course!

Visit

https://support.apple.com/en-gb/guide/icloud/mm6b1a490a/icloud

for details