how do I transfer my purchases from one account to the other?

You can’t. Two Apple IDs can’t be merged.

If you had issues with your original ID, resolve those issues instead of creating a new one. For example, you can change your email, account name and password.

Follow these steps to change the email address or phone number that you use as your Apple ID.

https://support.apple.com/en-us/HT202667

You can change or reset the password for your Apple ID account by providing some information. Reset your password here.  

What to do after you change your Apple ID or password - Apple Support

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

You can try setting up Family Sharing between the IDs if you want to be able to share purchases made with the IDs.

Family Sharing.         

Family Sharing - Set up.