Migrate website by .wpress

Dear sirs,
I’m a beginner making a big mistake of using all-in-one migration to export my website to a whole package(a “.wpress” file, containing old database information inside) unless using separated database files and then restored it on my new host.
After that my website display”Error establishing a database connection”.
I have tried checking the config.php, but the database name is correct to my new host.
I now understand that’ s a terrible way to migrate my web, however, I don’t have any backup. Is there any method can help save this problem?

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