Hello
Some days ago, I have converted my Website ASP into HTML.
I am scared that will be bad to google SEO.
Whether to have an impact on SEO ?
How to reduce the negative impact ?
Could you please give some advice ?
Thanks

If your page names are unchanged, then that will minimize the Google impact.

If not, put pages with old names in your new site and configure them to "permanently redirect" to the corresponding new page. That is in the Advanced Settings, Other Settings section of Page Settings for the page.