English to Spanish Bus/Financial Engineering: Industrial Machine description

Hello everyone.

The term I am looking for in Spanish I know the translation, but I am not quite sure about the correct spelling. Can anyone helps please? I have looked on the Internet but could not find a reliable source. Any Spanish linguist or Filólogo?

So the original term is:
Pre-assembled

Translation and correct spelling would be....

Pre-montado- One word and a hypphen

or

pre montado- two words and no hyphen in between



Many thanks in advance.