Hi Wei,
It is highly likely that your Minecraft account was successfully migrated to a different Microsoft email address that you have simply forgotten. During the mandatory migration from Mojang accounts to Microsoft accounts, users had to link their game license to a Microsoft email []. The email you are checking now might be an old one you used for Mojang but isn't the final Microsoft account that holds the license now.
Your username "TrySkillz" is a good piece of information, but the license is tied to the Microsoft email login.
What You Can Do Next is:
Use the Official Microsoft Account Recovery Form
This is the primary way to try and recover a forgotten email address linked to Microsoft services (like Minecraft/Xbox).
Go to the Microsoft Account Recovery Form.
The form asks for your email address. You will have to try every possible email address you might have used over the years (personal emails, old school emails, etc.).
Focus on providing as much information as possible from the past (past passwords, contacts, etc.).
Check Other Email Inboxes for Migration Confirmation
You mentioned having proof of purchase/migration. Go back to that email and look closely. It should mention which Microsoft email the account was successfully migrated to. Check all your other email inboxes (Gmail, Yahoo, iCloud, etc.) for a confirmation email with details of the new login.
Contact Minecraft Support Directly
This is your best option, as you have concrete proof of purchase and your username. The official Minecraft Support team has the tools to verify your ownership using your transaction ID.
Go to the Minecraft Help Center.
Select "Technical Support" or "Account Issues__"__ as the category.
Fill out the request form.
In the description, explain exactly what you told me: your username is "TrySkillz", you have proof of purchase/migration, but you forgot the Microsoft email it was linked to.
Attach your proof of purchase (the transaction ID or receipt from Mojang) to the ticket.
The support team should be able to track down which Microsoft account your username is currently attached to and guide you through the process of recovering that specific Microsoft email. Good luck, I hope you get back to your game soon!