How to copy powerpoint slides from an old template into a new one and take on the new template?

I want to copy powerpoint slides from an old template into a new one. I follow the steps at https://support.microsoft.com/en-us/office/copy-and-paste-your-slides-1fe39ace-4df6-4346-b724-30a6e2c0aeab but the slides still keep their original format. How can I copy just the text and layout, without background, to the new presentation?