Answer:
You may mean unum cum noris, omnes noris: "when you know one, you know them all", which is a line from the play Phormio by the Roman playwright Terence (Publius Terentius Afer). The version cited says "when you know one, you know one".
The line is more frequently cited as unum cognoris, omnes noris, "you become acquainted with one, you know them all". This is how the line appears in the edition of the play at the Perseus Digital Library (see link below).