Default transliteration · John
约翰 is not a name a native would pick
约翰 (Yuēhàn) is in every textbook, every church bulletin, every 'English names in Chinese' chart. That is the tell. A name that common as a spelling is not a name.
No surname, two foreign syllables
约 and 翰 are not doing 姓 + 名 work. There is no family name in first position. You cannot split 约翰 into a plausible Chinese personal name without leaving the language.
The 约翰·Smith pattern
Add a 间隔号 and you get the news-wire form: 约翰·史密斯. The middle dot is how mainland copy files a foreigner. If your 'Chinese name' wants that dot, it was never a Chinese name.
John can still have a Chinese name
费正清 (John Fairbank) is the historical reminder: a real surname, a literary given name, not 约翰. This site will not generate your version. It will tell you if the one you have is 约翰 in a trench coat.