Change (create new) apple email alias

You cannot change the prefix to any @icloud.com, @me.com nor any @mac.com. So you’ll have to use an alias to have a different email address to use.

Your @me.com is already nothing more than an alias to your iCloud inbox (iCloud: About your @icloud.com, @me.com, and @mac.com email addresses - Apple Support). But you can create another custom alias for your iCloud email.

See -> Use email aliases on iCloud.com - Apple Support

See the instructions below for changing an Apple ID.

Change your Apple ID  https://support.apple.com/en-us/HT202667 See this heading If your Apple ID is a third-party email address. It bears specifically on what you want to do--"you can ... [change to] an @icloud.com, @me.com, or @mac.com email address that's already a login alias or alternate Apple ID for your account." To see these addresses, sign into your Apple ID account page. 

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.”

And see What to do after you change your Apple ID or password 

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

I was saying "you can ... [change to] an @icloud.com, @me.com, or @mac.com email address that's already a login alias or alternate Apple ID for your account." To see these addresses, sign into your Apple ID account page."

But, you also can use one of those now presumably-- if you use the same preceding name. You also could create a new mac-type Apple ID to get the preceding name the way you want it. But doing so would create some problems. Post back if you are interested in this alternative.

Also beware that if you have an3rd party email address as your primary AppleID address and you change the primary to an @icloud.com, @me.com or @mac.com alias, you can never again use any 3rd party email address as the primary for that AppleID.

Change your Apple ID - Apple Support

“If you enter an email address that's already an alias or alternate Apple ID, and it ends with with @icloud.com, @me.com, or @mac.com, you see a message to confirm. When you change your Apple ID to an @icloud.com, @me.com, or @mac.com account, you can't change it back to a third-party email account. Your former Apple ID that ends with a third-party email becomes an additional email address for your Apple ID account.”

You are very welcome. Be safe.