how do i delete old user id account

Why not simply change the email address on that account? Everything you have done with that ID is tied to that ID; at best you can share some but in other cases it cannot be transferred.

Here's how you change the email address you use for your Apple ID:

1. Go to https://appleid.apple.com and sign in.

2. In the Sign-In and Security section, choose Apple ID.

3. Enter the email address that you want to use as your Apple ID.

4. Choose Change Apple ID.

5. If you changed your Apple ID to a third-party email address, check your email for a verification code, then enter the code. Learn what to do if you didn't get the email. --> If you didn't receive your verification or reset email - Apple Support

6. If you use services like iCloud or Messages to share with friends and colleagues, sign in to those services with your updated Apple ID. --> What to do after you change your Apple ID or password - Apple Support

For more details, and how to do this if you have a mobile number ID, see the document Change your Apple ID - Change your Apple ID - Apple Support

There's special instructions if you want to change your Apple ID to an @icloud.com address.

Take in mind that deleting your Apple ID is permanent, there is no recovery possible of the account after you've deleted it.

If you still want to delete it, follow these instructions

Sign in with your Apple ID at privacy.apple.com on a Mac, PC, iPhone, or iPad, and select “Request to delete your account”.

When you request account deletion, you'll receive a unique alphanumeric access code. Make sure that you keep this access code in a safe place. For a short period of time while your request is being processed, you can contact Apple Support, provide your access code, and we’ll help you cancel your request so you can resume using your Apple ID. 

How to delete your Apple ID account - Apple Support