Can I change a current sign in to an apple sign in?

Is your short sign in an Apple ID that isn't an email address? If so, you can try to do a name change to make your short sign in an email address. If that isn't what you mean, more information would help.

Note the restrictions in the article.

Apple ID Name Change

 What to do after you change your Apple ID or password - Apple Support     I suggest doing this before you change your Apple ID or password.