Asking about a text field to Embed Z coordinate user text in a block

My goal: I want to convert the results of the “Z-point Coordinate” (cm unit) which is in the viewport model into the viewport layout into units of “mm” according to the viewport layout unit. therefore I have tried to make the text field as drawn with the hope that the initial 200 cm will become 2000 mm. What is the right formula to answer this problem, sir?
Thank you very much for your time, I really appreciate it, may God bless.