I'm not sure what you're asking.

A website is simply a space on the internet which contains information.

Word is not a website. It's a word processing application.
A website is built with a HTML Editor or a
WYSIWYG application. What You See Is What You Get.
A WYSIWYG application is basically a word processor that automatically converts what you type into HTML code so it can be seen and read on your webpage.
Are you trying to build a website?
Are you trying to post on a website?

Hi,

Im looking for a website in which I can insert "This is my website" and it spits back "This-is-my-website"

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You can do that with any text editor that has a search and replace function. Notepad will do it. In Notepad:

1. Go to Edit/Replace
2. Type a space in the Find what field
3. Type a hyphen in the Replace with field
4. Click the Replace All button.

Done.