How do you change the sentence say this in English into form of What is this?

You can't directly change "Say this in English" into "What is this?". They express different meanings:

* "Say this in English" is a command asking someone to translate a word or phrase from another language into English.

* "What is this?" is a question asking for the identity or nature of something.

If you want to ask someone to identify something in English, you could say:

* "What is this called in English?"

* "What's the English word for this?"

* "Can you tell me what this is in English?"