when i enable "Allow Alert When Product Comes Back in Stock" on magneto admin backend and it shows "Notify me when this product is in stock" on product page. I want to edit the product alert text on front but how? i have no idea, please help!
You can turn on your Template Path Hints and see which file it is.
Check this link: https://docs.magento.com/user-guide/system/template-path-hints.html
And when you are editing you should follow Magento's best practice.
Template customization walkthrough
To customize a template:
Locate the template which is associated with the page/block you want to change using template hints.
Copy the template to your theme folder according to the template storing convention.
Make the required changes.
To add a new template in a theme:
Add a template in your theme directory according to the template storing convention.
Assign your template to a block in the corresponding layout file.
Actually there's another easier way which is Inline Translate.
Translating is simply just changing 1 text to another.
You can use Inline Translate or Translate using the i18n folder that Magento provided.
More information can be found here: https://devdocs.magento.com/guides/v2.4/frontend-dev-guide/translations/xlate.html