I want to use the name Amana for my daughter but I am not sure which way it is spelt correctly (Amana or Amanah). Could you please confirm how it is spelt and what meaning it has? Thank you

Both spellings are correct. Amana is an Arabic word, for this reason you can spell it any way you like. The important thing is how you pronounce it. In the original Arabic there is an h at the end, but when you say the name you do not pronounce the h, so there is no need to keep it in the English spelling. You can see its pronunciation and its many different spellings on this page: Amanah