Can PhD Thesis be converted into Three IEEE Journal Papers (same as they are in Thesis)?
You are mixing up a bunch of things here:

1. Copyright
Since you have the copyright to your text, there is no issue here. (Personal opinion: It is rarely necessary to pay much attention to copyright issues in academia anyway.)

2. Plagiarism Since you wrote that text, there is no plagiarism issue here. Even if the journal should check for coincides in the text, they will see that this text is written by you.

3. "Self-plagiarism" / Double-publication The former is very unfortunately named, since it is no case of plagiarism. The latter points out what the actual issue is. As a rule of thumb, this only applies to the same type of publication - having the same text in journal article and dissertation is fine. In this case, the subsequent publication should clearly mention the preceding one. So the journal articles would say prominently that they are based on Chapter X of your thesis.

4. Writing appropriately for the setting If your dissertation is actually written as a dissertation, then to make good journal articles out of it, probably significant rewriting would be necessary. This is because the style (e.g. level of detail) is different; because chapters of a dissertation can be more tightly coupled than different journal articles, etc.

If you fundamentally wrote three journal articles, did not publish those but stabled them together, this is not an issue. Then updating the references/context description would be enough.