The MI Fit App (Version 3.4.2 and higher) from the Google play store seem to support English language Now. However, some users have been complaining of the MI Band 3 language changing to Chinese as soon as you change your phone language from English to any other language. So you might want to leave your phone language in English.

I don't think you have a global version. So if you want it in English then leave your Phone on English and update if needed