Since this word is made up of a single kanji, it probably uses the kun'yomi reading. You did not learn this reading, so here's a mnemonic to help you to remember:
Do you know a Lord? Imagine it being someone named Mr. or Ms. Don (どの). If you know a Don, that's great, imagine that person. If you don't, think of a famous Don that's out there.
This certificate is awarded to Mr. Nakamura Koichi in recognition of his outstanding achievement.
Please tell Lord Suzuki.
The use of "dono" after a name is used today only in written documents as an honorific title for those who are equal or inferior to you.