"I want to thank everyone who works at the ABC organisation for their hard work"
--> 私はABC組合 / ABC協会 / ABC党のために一生懸命働いてくださるみなさんにお礼を申し上げたいです。
"Organization" can be translated in several ways depending on the situation in Japanese and now I don't know what you are mentioning, so I wrote three but there will be other translations. Please remember that there also be various ways of translations for this sentence in the different formality.
One more thing, I would say
誰か / どなたか、次の文章を翻訳するのを手伝ってくれませんか。よろしくお願いします。for "Can someone help me translate the following sentence? Thanks".
I hope this helps you.
*If you know English, putting your level on your profile would be much better.